diff --git a/macosx/coreaudio/JackCoreAudioAdapter.cpp b/macosx/coreaudio/JackCoreAudioAdapter.cpp
index e6711888..62ff1ad4 100644
--- a/macosx/coreaudio/JackCoreAudioAdapter.cpp
+++ b/macosx/coreaudio/JackCoreAudioAdapter.cpp
@@ -801,7 +801,7 @@ int JackCoreAudioAdapter::OpenAUHAL(bool capturing,
     }
     
     AudioDeviceID currAudioDeviceID;
-    UInt32 size;
+    UInt32 size = sizeof(AudioDeviceID);
     err1 = AudioUnitGetProperty(fAUHAL, kAudioOutputUnitProperty_CurrentDevice, kAudioUnitScope_Global, 0, &currAudioDeviceID, &size);
     if (err1 != noErr) {
         jack_error("Error calling AudioUnitGetProperty - kAudioOutputUnitProperty_CurrentDevice");
diff --git a/macosx/coreaudio/JackCoreAudioDriver.cpp b/macosx/coreaudio/JackCoreAudioDriver.cpp
index 9f0058ec..1b2a3bfb 100644
--- a/macosx/coreaudio/JackCoreAudioDriver.cpp
+++ b/macosx/coreaudio/JackCoreAudioDriver.cpp
@@ -683,7 +683,7 @@ int JackCoreAudioDriver::OpenAUHAL(bool capturing,
     }
     
     AudioDeviceID currAudioDeviceID;
-    UInt32 size;
+    UInt32 size = sizeof(AudioDeviceID);
     err1 = AudioUnitGetProperty(fAUHAL, kAudioOutputUnitProperty_CurrentDevice, kAudioUnitScope_Global, 0, &currAudioDeviceID, &size);
     if (err1 != noErr) {
         jack_error("Error calling AudioUnitGetProperty - kAudioOutputUnitProperty_CurrentDevice");