diff --git a/headers/os/midi/MidiSynth.h b/headers/os/midi/MidiSynth.h
index cf24322538..abf90c663c 100644
--- a/headers/os/midi/MidiSynth.h
+++ b/headers/os/midi/MidiSynth.h
@@ -7,6 +7,8 @@
 #include <Synth.h>
 #include <MidiDefs.h>
 
+class BSynth;
+
 class BMidiSynth : public BMidi
 {
 public:
diff --git a/headers/os/midi/Synth.h b/headers/os/midi/Synth.h
index 70775ac714..8ca71d9a64 100644
--- a/headers/os/midi/Synth.h
+++ b/headers/os/midi/Synth.h
@@ -87,8 +87,8 @@ public:
 
 private:
 
-	friend BMidiSynth;
-	friend BMidiSynthFile;
+	friend class BMidiSynth;
+	friend class BMidiSynthFile;
 
 	virtual void _ReservedSynth1();
 	virtual void _ReservedSynth2();
diff --git a/src/kits/midi/MidiSynth.cpp b/src/kits/midi/MidiSynth.cpp
index f2a991c81c..7e808ecebc 100644
--- a/src/kits/midi/MidiSynth.cpp
+++ b/src/kits/midi/MidiSynth.cpp
@@ -21,8 +21,9 @@
  * DEALINGS IN THE SOFTWARE.
  */
 
+#include <MidiSynth.h>
+
 #include "debug.h"
-#include "MidiSynth.h"
 #include "SoftSynth.h"
 
 using namespace BPrivate;
diff --git a/src/kits/midi/SoftSynth.h b/src/kits/midi/SoftSynth.h
index 78482acd5c..46c0bbfce9 100644
--- a/src/kits/midi/SoftSynth.h
+++ b/src/kits/midi/SoftSynth.h
@@ -59,6 +59,8 @@
 
 class BMidiConsumer;
 class BMidiLocalProducer;
+class BMidiSynth;
+class BSynth;
 
 namespace BPrivate {
 
@@ -118,8 +120,8 @@ public:
 
 private:
 
-	friend class BSynth;
-	friend class BMidiSynth;
+	friend class ::BSynth;
+	friend class ::BMidiSynth;
 
 	BSoftSynth();
 	~BSoftSynth();
diff --git a/src/kits/midi2/MidiRosterLooper.h b/src/kits/midi2/MidiRosterLooper.h
index ed79591f81..284c0e7fba 100644
--- a/src/kits/midi2/MidiRosterLooper.h
+++ b/src/kits/midi2/MidiRosterLooper.h
@@ -26,6 +26,7 @@
 #include <Looper.h>
 #include <Message.h>
 
+class BMidiProducer;
 class BMidiRoster;
 
 namespace BPrivate {
@@ -71,8 +72,8 @@ public:
 	
 private:
 
-	friend class BMidiRoster;
-	friend class BMidiProducer;
+	friend class ::BMidiRoster;
+	friend class ::BMidiProducer;
 
 	typedef BLooper super;