diff --git a/build/win32/platform_specific_code/juce_win32_DirectSound.cpp b/build/win32/platform_specific_code/juce_win32_DirectSound.cpp
index 2e414e6075..79f7a85b90 100644
--- a/build/win32/platform_specific_code/juce_win32_DirectSound.cpp
+++ b/build/win32/platform_specific_code/juce_win32_DirectSound.cpp
@@ -1612,13 +1612,13 @@ const String DSoundAudioIODevice::openDevice (const BitArray& inputChannels,
     dlh.scanForDevices();
 
     enabledInputs = inputChannels;
-    enabledInputs.setRange (inChannels.size(),
-                            enabledInputs.getHighestBit() + 1 - inChannels.size(),
-                            false);
-
+    enabledInputs.setRange (inChannels.size(),
+                            enabledInputs.getHighestBit() + 1 - inChannels.size(),
+                            false);
+
     numInputBuffers = enabledInputs.countNumberOfSetBits();
     inputBuffers = new float* [numInputBuffers + 2];
-    zeromem (inputBuffers, sizeof (inputBuffers));
+    zeromem (inputBuffers, sizeof (float*) * numInputBuffers + 2);
     int i, numIns = 0;
 
     for (i = 0; i <= enabledInputs.getHighestBit(); i += 2)
@@ -1640,13 +1640,13 @@ const String DSoundAudioIODevice::openDevice (const BitArray& inputChannels,
     }
 
     enabledOutputs = outputChannels;
-    enabledOutputs.setRange (outChannels.size(),
-                             enabledOutputs.getHighestBit() + 1 - outChannels.size(),
-                             false);
+    enabledOutputs.setRange (outChannels.size(),
+                             enabledOutputs.getHighestBit() + 1 - outChannels.size(),
+                             false);
 
     numOutputBuffers = enabledOutputs.countNumberOfSetBits();
     outputBuffers = new float* [numOutputBuffers + 2];
-    zeromem (outputBuffers, sizeof (outputBuffers));
+    zeromem (outputBuffers, sizeof (float*) * numOutputBuffers + 2);
     int numOuts = 0;
 
     for (i = 0; i <= enabledOutputs.getHighestBit(); i += 2)