diff --git a/libs/ardour/ardour/audio_unit.h b/libs/ardour/ardour/audio_unit.h
index 48ea614f8e..13b16827cb 100644
--- a/libs/ardour/ardour/audio_unit.h
+++ b/libs/ardour/ardour/audio_unit.h
@@ -53,9 +53,8 @@ struct LIBARDOUR_API AUParameterDescriptor : public ParameterDescriptor {
 	AudioUnitParameterID id;
 	AudioUnitScope scope;
 	AudioUnitElement element;
-	float default_value;
 	bool automatable;
-	AudioUnitParameterUnit unit;
+	AudioUnitParameterUnit au_unit;
 };
 
 class LIBARDOUR_API AUPlugin : public ARDOUR::Plugin
diff --git a/libs/ardour/audio_unit.cc b/libs/ardour/audio_unit.cc
index 21f2a78be0..820f41061b 100644
--- a/libs/ardour/audio_unit.cc
+++ b/libs/ardour/audio_unit.cc
@@ -606,7 +606,7 @@ AUPlugin::discover_parameters ()
 
 			d.lower = info.minValue;
 			d.upper = info.maxValue;
-			d.default_value = info.defaultValue;
+			d.normal = info.defaultValue;
 
 			d.integer_step = (info.unit == kAudioUnitParameterUnit_Indexed);
 			d.toggled = (info.unit == kAudioUnitParameterUnit_Boolean) ||
@@ -617,7 +617,18 @@ AUPlugin::discover_parameters ()
 				(info.flags & kAudioUnitParameterFlag_IsWritable);
 
 			d.logarithmic = (info.flags & kAudioUnitParameterFlag_DisplayLogarithmic);
-			d.unit = info.unit;
+			d.au_unit = info.unit;
+			switch (info.unit) {
+			case kAudioUnitParameterUnit_Decibels:
+				d.unit = ParameterDescriptor::DB;
+				break;
+			case kAudioUnitParameterUnit_MIDINoteNumber:
+				d.unit = ParameterDescriptor::MIDI_NOTE;
+				break;
+			case kAudioUnitParameterUnit_Hertz:
+				d.unit = ParameterDescriptor::HZ;
+				break;
+			}
 
 			d.min_unbound = 0; // lower is bound
 			d.max_unbound = 0; // upper is bound
@@ -759,7 +770,7 @@ float
 AUPlugin::default_value (uint32_t port)
 {
 	if (port < descriptors.size()) {
-		return descriptors[port].default_value;
+		return descriptors[port].normal;
 	}
 
 	return 0;