diff --git a/source/Makefile.mk b/source/Makefile.mk
index a9e2bf4b7..8ed9a19c1 100644
--- a/source/Makefile.mk
+++ b/source/Makefile.mk
@@ -54,6 +54,7 @@ BUILD_CXX_FLAGS += -DVESTIGE_HEADER
 
 HAVE_JACK         = $(shell pkg-config --exists jack && echo true)
 HAVE_OPENGL       = $(shell pkg-config --exists gl && echo true)
+HAVE_QT5          = $(shell pkg-config --atleast-version=5.0 QtCore && echo true)
 
 HAVE_AF_DEPS      = $(shell pkg-config --exists libavcodec libavformat sndfile && echo true)
 HAVE_ZYN_DEPS     = $(shell pkg-config --exists fftw3 mxml zlib && echo true)
diff --git a/source/backend/engine/CarlaEngine.cpp b/source/backend/engine/CarlaEngine.cpp
index 20148aefb..cbd90867b 100644
--- a/source/backend/engine/CarlaEngine.cpp
+++ b/source/backend/engine/CarlaEngine.cpp
@@ -1033,6 +1033,10 @@ bool CarlaEngine::loadProject(const char* const filename)
         if (node.toElement().tagName() == "Plugin")
         {
             const SaveState& saveState = getSaveStateDictFromXML(node);
+            CARLA_ASSERT(saveState.type != nullptr);
+
+            if (saveState.type == nullptr)
+                continue;
 
             const void* extraStuff = nullptr;
 
diff --git a/source/backend/plugin/BridgePlugin.cpp b/source/backend/plugin/BridgePlugin.cpp
index 2205db15a..671a9ec40 100644
--- a/source/backend/plugin/BridgePlugin.cpp
+++ b/source/backend/plugin/BridgePlugin.cpp
@@ -914,6 +914,26 @@ public:
 
     bool init(const char* const filename, const char* const name, const char* const label, const char* const bridgeBinary)
     {
+        // ---------------------------------------------------------------
+        // first checks
+
+        if (kData->engine == nullptr)
+        {
+            return false;
+        }
+
+        if (kData->client != nullptr)
+        {
+            kData->engine->setLastError("Plugin client is already registered");
+            return false;
+        }
+
+        if (filename == nullptr)
+        {
+            kData->engine->setLastError("null filename");
+            return false;
+        }
+
         m_filename = strdup(filename);
 
         if (name)
diff --git a/source/backend/plugin/CarlaPlugin.cpp b/source/backend/plugin/CarlaPlugin.cpp
index a66abe762..4101443b9 100644
--- a/source/backend/plugin/CarlaPlugin.cpp
+++ b/source/backend/plugin/CarlaPlugin.cpp
@@ -655,7 +655,7 @@ void CarlaPlugin::loadSaveState(const SaveState& saveState)
 
     QVector<ParamSymbol> paramSymbols;
 
-    if (std::strcmp(saveState.type, "LADSPA") == 0 || std::strcmp(saveState.type, "LV2") == 0)
+    if (type() == PLUGIN_LADSPA || type() == PLUGIN_LV2)
     {
         for (uint32_t i=0; i < kData->param.count; i++)
         {
@@ -680,7 +680,7 @@ void CarlaPlugin::loadSaveState(const SaveState& saveState)
 
         int32_t index = -1;
 
-        if (std::strcmp(saveState.type, "LADSPA") == 0)
+        if (type() == PLUGIN_LADSPA)
         {
             // Try to set by symbol, otherwise use index
             if (stateParameter->symbol != nullptr && *stateParameter->symbol != 0)
@@ -699,7 +699,7 @@ void CarlaPlugin::loadSaveState(const SaveState& saveState)
             else
                 index = stateParameter->index;
         }
-        else if (std::strcmp(saveState.type, "LV2") == 0)
+        else if (type() == PLUGIN_LV2)
         {
             // Symbol only
             if (stateParameter->symbol != nullptr && *stateParameter->symbol != 0)
@@ -1178,6 +1178,13 @@ void CarlaPlugin::setCustomData(const char* const type, const char* const key, c
             CARLA_ASSERT(cData.key != nullptr);
             CARLA_ASSERT(cData.value != nullptr);
 
+            if (cData.type == nullptr)
+                return;
+            if (cData.key == nullptr)
+                return;
+            if (cData.value == nullptr)
+                return;
+
             if (std::strcmp(cData.key, key) == 0)
             {
                 if (cData.value != nullptr)
@@ -1926,6 +1933,15 @@ CarlaPlugin::ScopedDisabler::ScopedDisabler(CarlaPlugin* const plugin)
 {
     carla_debug("CarlaPlugin::ScopedDisabler(%p)", plugin);
     CARLA_ASSERT(plugin != nullptr);
+    CARLA_ASSERT(plugin->kData != nullptr);
+    CARLA_ASSERT(plugin->kData->client != nullptr);
+
+    if (plugin == nullptr)
+        return;
+    if (plugin->kData == nullptr)
+        return;
+    if (plugin->kData->client == nullptr)
+        return;
 
     plugin->kData->masterMutex.lock();
 
@@ -1939,6 +1955,16 @@ CarlaPlugin::ScopedDisabler::ScopedDisabler(CarlaPlugin* const plugin)
 CarlaPlugin::ScopedDisabler::~ScopedDisabler()
 {
     carla_debug("CarlaPlugin::~ScopedDisabler()");
+    CARLA_ASSERT(kPlugin != nullptr);
+    CARLA_ASSERT(kPlugin->kData != nullptr);
+    CARLA_ASSERT(kPlugin->kData->client != nullptr);
+
+    if (kPlugin == nullptr)
+        return;
+    if (kPlugin->kData == nullptr)
+        return;
+    if (kPlugin->kData->client == nullptr)
+        return;
 
     kPlugin->fEnabled = true;
     kPlugin->kData->client->activate();
@@ -1955,13 +1981,19 @@ CarlaPlugin::ScopedProcessLocker::ScopedProcessLocker(CarlaPlugin* const plugin,
     carla_debug("CarlaPlugin::ScopedProcessLocker(%p, %s)", plugin, bool2str(block));
     CARLA_ASSERT(plugin != nullptr);
 
-    if (block)
+    if (plugin != nullptr && block)
         plugin->kData->singleMutex.lock();
 }
 
 CarlaPlugin::ScopedProcessLocker::~ScopedProcessLocker()
 {
     carla_debug("CarlaPlugin::~ScopedProcessLocker()");
+    CARLA_ASSERT(kPlugin != nullptr && kPlugin->kData != nullptr);
+
+    if (kPlugin == nullptr)
+        return;
+    if (kPlugin->kData == nullptr)
+        return;
 
     if (kBlock)
     {
@@ -2005,6 +2037,14 @@ void CarlaPluginGUI::idle()
 
 void CarlaPluginGUI::resizeLater(int width, int height)
 {
+    CARLA_ASSERT_INT(width > 0, width);
+    CARLA_ASSERT_INT(height > 0, height);
+
+    if (width <= 0)
+        return;
+    if (height <= 0)
+        return;
+
     fNextWidth  = width;
     fNextHeight = height;
 }
@@ -2047,6 +2087,9 @@ void CarlaPluginGUI::closeEvent(QCloseEvent* const event)
     carla_debug("CarlaPluginGUI::closeEvent(%p)", event);
     CARLA_ASSERT(event != nullptr);
 
+    if (event == nullptr)
+        return;
+
     if (! event->spontaneous())
     {
         event->ignore();
diff --git a/source/backend/plugin/DssiPlugin.cpp b/source/backend/plugin/DssiPlugin.cpp
index 43796d1fc..a7bac7618 100644
--- a/source/backend/plugin/DssiPlugin.cpp
+++ b/source/backend/plugin/DssiPlugin.cpp
@@ -370,8 +370,18 @@ public:
         carla_debug("DssiPlugin::reload() - start");
         CARLA_ASSERT(kData->engine != nullptr);
         CARLA_ASSERT(fDescriptor != nullptr);
+        CARLA_ASSERT(fDssiDescriptor != nullptr);
         CARLA_ASSERT(fHandle != nullptr);
 
+        if (kData->engine == nullptr)
+            return;
+        if (fDescriptor == nullptr)
+            return;
+        if (fDssiDescriptor == nullptr)
+            return;
+        if (fHandle == nullptr)
+            return;
+
         const ProcessMode processMode(kData->engine->getProccessMode());
 
         // Safely disable plugin for reload
@@ -1065,8 +1075,9 @@ public:
                 {
                     if (processSingle(inBuffer, outBuffer, time - timeOffset, timeOffset, midiEventCount))
                     {
-                        midiEventCount = 0;
+                        startTime  = 0;
                         timeOffset = time;
+                        midiEventCount = 0;
 
                         if (kData->midiprog.current >= 0 && kData->midiprog.count > 0)
                             nextBankId = kData->midiprog.data[kData->midiprog.current].bank;
@@ -1434,6 +1445,24 @@ public:
 
     bool processSingle(float** const inBuffer, float** const outBuffer, const uint32_t frames, const uint32_t timeOffset, const unsigned long midiEventCount)
     {
+        CARLA_ASSERT(frames > 0);
+
+        if (frames == 0)
+            return false;
+
+        if (kData->audioIn.count > 0)
+        {
+            CARLA_ASSERT(inBuffer != nullptr);
+            if (inBuffer == nullptr)
+                return false;
+        }
+        if (kData->audioOut.count > 0)
+        {
+            CARLA_ASSERT(outBuffer != nullptr);
+            if (outBuffer == nullptr)
+                return false;
+        }
+
         uint32_t i, k;
 
         // --------------------------------------------------------------------------------------------------------
@@ -1748,6 +1777,32 @@ public:
         CARLA_ASSERT(filename != nullptr);
         CARLA_ASSERT(label != nullptr);
 
+        // ---------------------------------------------------------------
+        // first checks
+
+        if (kData->engine == nullptr)
+        {
+            return false;
+        }
+
+        if (kData->client != nullptr)
+        {
+            kData->engine->setLastError("Plugin client is already registered");
+            return false;
+        }
+
+        if (filename == nullptr)
+        {
+            kData->engine->setLastError("null filename");
+            return false;
+        }
+
+        if (label == nullptr)
+        {
+            kData->engine->setLastError("null label");
+            return false;
+        }
+
         // ---------------------------------------------------------------
         // open DLL
 
diff --git a/source/backend/plugin/FluidSynthPlugin.cpp b/source/backend/plugin/FluidSynthPlugin.cpp
index 9ba7ce180..798d6421d 100644
--- a/source/backend/plugin/FluidSynthPlugin.cpp
+++ b/source/backend/plugin/FluidSynthPlugin.cpp
@@ -392,6 +392,11 @@ public:
         CARLA_ASSERT(kData->engine != nullptr);
         CARLA_ASSERT(fSynth != nullptr);
 
+        if (kData->engine == nullptr)
+            return;
+        if (fSynth == nullptr)
+            return;
+
         const ProcessMode processMode(kData->engine->getProccessMode());
 
         // Safely disable plugin for reload
@@ -957,6 +962,7 @@ public:
                 {
                     if (processSingle(outBuffer, time - timeOffset, timeOffset))
                     {
+                        startTime  = 0;
                         timeOffset = time;
 
                         if (kData->midiprog.current >= 0 && kData->midiprog.count > 0 && kData->ctrlChannel >= 0 && kData->ctrlChannel < 16)
@@ -1233,6 +1239,14 @@ public:
 
     bool processSingle(float** const outBuffer, const uint32_t frames, const uint32_t timeOffset)
     {
+        CARLA_ASSERT(outBuffer != nullptr);
+        CARLA_ASSERT(frames > 0);
+
+        if (outBuffer == nullptr)
+            return false;
+        if (frames == 0)
+            return false;
+
         uint32_t i, k;
 
         // --------------------------------------------------------------------------------------------------------
@@ -1373,6 +1387,38 @@ public:
         CARLA_ASSERT(filename != nullptr);
         CARLA_ASSERT(label != nullptr);
 
+        // ---------------------------------------------------------------
+        // first checks
+
+        if (kData->engine == nullptr)
+        {
+            return false;
+        }
+
+        if (kData->client != nullptr)
+        {
+            kData->engine->setLastError("Plugin client is already registered");
+            return false;
+        }
+
+        if (fSynth == nullptr)
+        {
+            kData->engine->setLastError("null synth");
+            return false;
+        }
+
+        if (filename == nullptr)
+        {
+            kData->engine->setLastError("null filename");
+            return false;
+        }
+
+        if (label == nullptr)
+        {
+            kData->engine->setLastError("null label");
+            return false;
+        }
+
         // ---------------------------------------------------------------
         // open soundfont
 
diff --git a/source/backend/plugin/LadspaPlugin.cpp b/source/backend/plugin/LadspaPlugin.cpp
index f081e9490..e8730d753 100644
--- a/source/backend/plugin/LadspaPlugin.cpp
+++ b/source/backend/plugin/LadspaPlugin.cpp
@@ -368,6 +368,13 @@ public:
         CARLA_ASSERT(fDescriptor != nullptr);
         CARLA_ASSERT(fHandle != nullptr);
 
+        if (kData->engine == nullptr)
+            return;
+        if (fDescriptor == nullptr)
+            return;
+        if (fHandle == nullptr)
+            return;
+
         const ProcessMode processMode(kData->engine->getProccessMode());
 
         // Safely disable plugin for reload
@@ -1078,6 +1085,24 @@ public:
 
     bool processSingle(float** const inBuffer, float** const outBuffer, const uint32_t frames, const uint32_t timeOffset)
     {
+        CARLA_ASSERT(frames > 0);
+
+        if (frames == 0)
+            return false;
+
+        if (kData->audioIn.count > 0)
+        {
+            CARLA_ASSERT(inBuffer != nullptr);
+            if (inBuffer == nullptr)
+                return false;
+        }
+        if (kData->audioOut.count > 0)
+        {
+            CARLA_ASSERT(outBuffer != nullptr);
+            if (outBuffer == nullptr)
+                return false;
+        }
+
         uint32_t i, k;
 
         // --------------------------------------------------------------------------------------------------------
@@ -1305,6 +1330,32 @@ public:
         CARLA_ASSERT(filename != nullptr);
         CARLA_ASSERT(label != nullptr);
 
+        // ---------------------------------------------------------------
+        // first checks
+
+        if (kData->engine == nullptr)
+        {
+            return false;
+        }
+
+        if (kData->client != nullptr)
+        {
+            kData->engine->setLastError("Plugin client is already registered");
+            return false;
+        }
+
+        if (filename == nullptr)
+        {
+            kData->engine->setLastError("null filename");
+            return false;
+        }
+
+        if (label == nullptr)
+        {
+            kData->engine->setLastError("null label");
+            return false;
+        }
+
         // ---------------------------------------------------------------
         // open DLL
 
diff --git a/source/backend/plugin/LinuxSamplerPlugin.cpp b/source/backend/plugin/LinuxSamplerPlugin.cpp
index d1724ee28..133ea8c51 100644
--- a/source/backend/plugin/LinuxSamplerPlugin.cpp
+++ b/source/backend/plugin/LinuxSamplerPlugin.cpp
@@ -301,6 +301,11 @@ public:
         CARLA_ASSERT(kData->engine != nullptr);
         CARLA_ASSERT(fInstrument != nullptr);
 
+        if (kData->engine == nullptr)
+            return;
+        if (fInstrument == nullptr)
+            return;
+
         const ProcessMode processMode(kData->engine->getProccessMode());
 
         // Safely disable plugin for reload
@@ -544,6 +549,7 @@ public:
                 {
                     if (processSingle(outBuffer, time - timeOffset, timeOffset))
                     {
+                        startTime  = 0;
                         timeOffset = time;
 
                         if (kData->midiprog.current >= 0 && kData->midiprog.count > 0)
@@ -803,6 +809,14 @@ public:
 
     bool processSingle(float** const outBuffer, const uint32_t frames, const uint32_t timeOffset)
     {
+        CARLA_ASSERT(outBuffer != nullptr);
+        CARLA_ASSERT(frames > 0);
+
+        if (outBuffer == nullptr)
+            return false;
+        if (frames == 0)
+            return false;
+
         uint32_t i, k;
 
         // --------------------------------------------------------------------------------------------------------
@@ -893,6 +907,32 @@ public:
         CARLA_ASSERT(filename != nullptr);
         CARLA_ASSERT(label != nullptr);
 
+        // ---------------------------------------------------------------
+        // first checks
+
+        if (kData->engine == nullptr)
+        {
+            return false;
+        }
+
+        if (kData->client != nullptr)
+        {
+            kData->engine->setLastError("Plugin client is already registered");
+            return false;
+        }
+
+        if (filename == nullptr)
+        {
+            kData->engine->setLastError("null filename");
+            return false;
+        }
+
+        if (label == nullptr)
+        {
+            kData->engine->setLastError("null label");
+            return false;
+        }
+
         // ---------------------------------------------------------------
         // Check if file exists
         {
diff --git a/source/backend/plugin/Lv2Plugin.cpp b/source/backend/plugin/Lv2Plugin.cpp
index 3e7d57578..da995b892 100644
--- a/source/backend/plugin/Lv2Plugin.cpp
+++ b/source/backend/plugin/Lv2Plugin.cpp
@@ -3937,6 +3937,26 @@ public:
 
     bool init(const char* const bundle, const char* const name, const char* const URI)
     {
+        // ---------------------------------------------------------------
+        // first checks
+
+        if (kData->engine == nullptr)
+        {
+            return false;
+        }
+
+        if (kData->client != nullptr)
+        {
+            kData->engine->setLastError("Plugin client is already registered");
+            return false;
+        }
+
+        if (filename == nullptr)
+        {
+            kData->engine->setLastError("null filename");
+            return false;
+        }
+
         // ---------------------------------------------------------------
         // get plugin from lv2_rdf (lilv)
 
diff --git a/source/backend/plugin/NativePlugin.cpp b/source/backend/plugin/NativePlugin.cpp
index 8bf7f3efa..0b8f59bd8 100644
--- a/source/backend/plugin/NativePlugin.cpp
+++ b/source/backend/plugin/NativePlugin.cpp
@@ -266,6 +266,9 @@ public:
     {
         CARLA_ASSERT(fDescriptor != nullptr);
 
+        if (fDescriptor == nullptr)
+            return 0x0;
+
         unsigned int options = 0x0;
 
         if (fDescriptor->name != nullptr)
@@ -619,6 +622,13 @@ public:
         CARLA_ASSERT(fDescriptor != nullptr);
         CARLA_ASSERT(fHandle != nullptr);
 
+        if (kData->engine == nullptr)
+            return;
+        if (fDescriptor == nullptr)
+            return;
+        if (fHandle == nullptr)
+            return;
+
         const ProcessMode processMode(kData->engine->getProccessMode());
 
         // Safely disable plugin for reload
@@ -1237,14 +1247,15 @@ public:
                 {
                     if (processSingle(inBuffer, outBuffer, time - timeOffset, timeOffset))
                     {
+                        startTime  = 0;
+                        timeOffset = time;
+                        nextBankId = 0;
+
                         if (fMidiEventCount > 0)
                         {
                             //carla_zeroMem(fMidiEvents, sizeof(::MidiEvent)*fMidiEventCount);
                             fMidiEventCount = 0;
                         }
-
-                        nextBankId = 0;
-                        timeOffset = time;
                     }
                     else
                         startTime += timeOffset;
@@ -1555,6 +1566,24 @@ public:
 
     bool processSingle(float** const inBuffer, float** const outBuffer, const uint32_t frames, const uint32_t timeOffset)
     {
+        CARLA_ASSERT(frames > 0);
+
+        if (frames == 0)
+            return false;
+
+        if (kData->audioIn.count > 0)
+        {
+            CARLA_ASSERT(inBuffer != nullptr);
+            if (inBuffer == nullptr)
+                return false;
+        }
+        if (kData->audioOut.count > 0)
+        {
+            CARLA_ASSERT(outBuffer != nullptr);
+            if (outBuffer == nullptr)
+                return false;
+        }
+
         uint32_t i, k;
 
         // --------------------------------------------------------------------------------------------------------
@@ -1930,7 +1959,27 @@ public:
     {
         CARLA_ASSERT(kData->engine != nullptr);
         CARLA_ASSERT(kData->client == nullptr);
-        CARLA_ASSERT(label);
+        CARLA_ASSERT(label != nullptr);
+
+        // ---------------------------------------------------------------
+        // first checks
+
+        if (kData->engine == nullptr)
+        {
+            return false;
+        }
+
+        if (kData->client != nullptr)
+        {
+            kData->engine->setLastError("Plugin client is already registered");
+            return false;
+        }
+
+        if (label == nullptr)
+        {
+            kData->engine->setLastError("null label");
+            return false;
+        }
 
         // ---------------------------------------------------------------
         // get descriptor that matches label
diff --git a/source/backend/plugin/VstPlugin.cpp b/source/backend/plugin/VstPlugin.cpp
index 213085641..a6d72c81b 100644
--- a/source/backend/plugin/VstPlugin.cpp
+++ b/source/backend/plugin/VstPlugin.cpp
@@ -168,6 +168,9 @@ public:
     {
         CARLA_ASSERT(fEffect != nullptr);
 
+        if (fEffect == nullptr)
+            return 0x0;
+
         unsigned int options = 0x0;
 
         options |= PLUGIN_OPTION_FIXED_BUFFER;
@@ -286,7 +289,9 @@ public:
         CARLA_ASSERT(parameterId < kData->param.count);
 
         const float fixedValue = kData->param.fixValue(parameterId, value);
-        fEffect->setParameter(fEffect, parameterId, fixedValue);
+
+        if (fEffect != nullptr)
+            fEffect->setParameter(fEffect, parameterId, fixedValue);
 
         CarlaPlugin::setParameterValue(parameterId, fixedValue, sendGui, sendOsc, sendCallback);
     }
@@ -431,6 +436,11 @@ public:
         CARLA_ASSERT(kData->engine != nullptr);
         CARLA_ASSERT(fEffect != nullptr);
 
+        if (kData->engine == nullptr)
+            return;
+        if (fEffect == nullptr)
+            return;
+
         const ProcessMode processMode(kData->engine->getProccessMode());
 
         // Safely disable plugin for reload
@@ -1085,13 +1095,14 @@ public:
                 {
                     if (processSingle(inBuffer, outBuffer, time - timeOffset, timeOffset))
                     {
+                        startTime  = 0;
+                        timeOffset = time;
+
                         if (fMidiEventCount > 0)
                         {
                             //carla_zeroMem(fMidiEvents, sizeof(::MidiEvent)*fMidiEventCount);
                             fMidiEventCount = 0;
                         }
-
-                        timeOffset = time;
                     }
                     else
                         startTime += timeOffset;
@@ -1367,6 +1378,24 @@ public:
 
     bool processSingle(float** const inBuffer, float** const outBuffer, const uint32_t frames, const uint32_t timeOffset)
     {
+        CARLA_ASSERT(frames > 0);
+
+        if (frames == 0)
+            return false;
+
+        if (kData->audioIn.count > 0)
+        {
+            CARLA_ASSERT(inBuffer != nullptr);
+            if (inBuffer == nullptr)
+                return false;
+        }
+        if (kData->audioOut.count > 0)
+        {
+            CARLA_ASSERT(outBuffer != nullptr);
+            if (outBuffer == nullptr)
+                return false;
+        }
+
         uint32_t i, k;
 
         // --------------------------------------------------------------------------------------------------------
@@ -2017,6 +2046,26 @@ public:
         CARLA_ASSERT(kData->client == nullptr);
         CARLA_ASSERT(filename != nullptr);
 
+        // ---------------------------------------------------------------
+        // first checks
+
+        if (kData->engine == nullptr)
+        {
+            return false;
+        }
+
+        if (kData->client != nullptr)
+        {
+            kData->engine->setLastError("Plugin client is already registered");
+            return false;
+        }
+
+        if (filename == nullptr)
+        {
+            kData->engine->setLastError("null filename");
+            return false;
+        }
+
         // ---------------------------------------------------------------
         // open DLL
 
diff --git a/source/bridges/Makefile b/source/bridges/Makefile
index 287c056d5..2133e08ff 100644
--- a/source/bridges/Makefile
+++ b/source/bridges/Makefile
@@ -30,16 +30,13 @@ LINK_FLAGS      += $(shell pkg-config --libs liblo QtCore)
 # Plugin bridges
 
 BUILD_PLUGIN_FLAGS  = $(BUILD_CXX_FLAGS)
-BUILD_PLUGIN_FLAGS += -DBUILD_BRIDGE_PLUGIN -DBRIDGE_PLUGIN -DWANT_JACK
+BUILD_PLUGIN_FLAGS += -DBUILD_BRIDGE_PLUGIN -DBRIDGE_PLUGIN
+BUILD_PLUGIN_FLAGS += -DWANT_LADSPA -DWANT_DSSI -DWANT_LV2 -DWANT_VST -DWANT_JACK
 BUILD_PLUGIN_FLAGS += -I../backend/engine -I../backend/plugin -I../libs
-BUILD_PLUGIN_FLAGS += $(shell pkg-config --cflags QtGui QtXml)
+BUILD_PLUGIN_FLAGS += $(QT_UI_FLAGS) $(shell pkg-config --cflags QtXml)
 
 LINK_PLUGIN_FLAGS   = $(LINK_FLAGS)
-LINK_PLUGIN_FLAGS  += $(shell pkg-config --libs QtGui QtXml) -lpthread
-
-ifeq ($(CARLA_PLUGIN_SUPPORT),true)
-BUILD_PLUGIN_FLAGS += -DWANT_LADSPA -DWANT_DSSI -DWANT_LV2 -DWANT_VST
-endif
+LINK_PLUGIN_FLAGS  += $(QT_UI_FLAGS) $(shell pkg-config --libs QtXml) -lpthread
 
 # --------------------------------------------------------------
 # Plugin bridges (POSIX)
@@ -65,11 +62,13 @@ NATIVE_LINK_FLAGS   = $(POSIX_LINK_FLAGS)
 
 ifeq ($(HAVE_FLUIDSYNTH),true)
 NATIVE_BUILD_FLAGS += -DWANT_FLUIDSYNTH
+NATIVE_BUILD_FLAGS += $(shell pkg-config --cflags fluidsynth)
 NATIVE_LINK_FLAGS  += $(shell pkg-config --libs fluidsynth)
 endif
 
 ifeq ($(HAVE_LINUXSAMPLER),true)
 NATIVE_BUILD_FLAGS += -DWANT_LINUXSAMPLER
+NATIVE_BUILD_FLAGS += $(shell pkg-config --cflags linuxsampler)
 NATIVE_LINK_FLAGS  += $(shell pkg-config --libs linuxsampler)
 endif
 
@@ -503,5 +502,6 @@ clean:
 	rm -f $(OBJS_POSIX64)
 	rm -f $(OBJS_WIN32)
 	rm -f $(OBJS_WIN64)
-	rm -f carla-bridge-lv2-gtk2 carla-bridge-lv2-gtk3 carla-bridge-lv2-qt4 carla-bridge-lv2-qt5 carla-bridge-lv2-x11 carla-bridge-vst-x11
+	rm -f carla-bridge-lv2-gtk2 carla-bridge-lv2-gtk3 carla-bridge-lv2-qt4 carla-bridge-lv2-qt5 carla-bridge-lv2-x11
+	rm -f carla-bridge-vst-x11
 	rm -f carla-bridge-native carla-bridge-posix32 carla-bridge-posix64