diff --git a/pa_common/portaudio.h b/pa_common/portaudio.h
index 35c2bcc..fe05829 100644
--- a/pa_common/portaudio.h
+++ b/pa_common/portaudio.h
@@ -131,7 +131,7 @@ typedef unsigned long PaSampleFormat;
 typedef int PaDeviceID;
 #define paNoDevice -1
 
-int Pa_CountDevices();
+int Pa_CountDevices( void );
 
 typedef struct
 {