diff --git a/src/gtk/app.cpp b/src/gtk/app.cpp
index 2c0b307922..418183b6e4 100644
--- a/src/gtk/app.cpp
+++ b/src/gtk/app.cpp
@@ -31,7 +31,10 @@
 #include "unistd.h"
 
 #ifdef __SUN__
-int usleep(unsigned int useconds); 
+extern "C" 
+{
+void usleep(unsigned long usec); 
+};
 #endif
 
 #include "glib.h"
diff --git a/src/gtk1/app.cpp b/src/gtk1/app.cpp
index 2c0b307922..418183b6e4 100644
--- a/src/gtk1/app.cpp
+++ b/src/gtk1/app.cpp
@@ -31,7 +31,10 @@
 #include "unistd.h"
 
 #ifdef __SUN__
-int usleep(unsigned int useconds); 
+extern "C" 
+{
+void usleep(unsigned long usec); 
+};
 #endif
 
 #include "glib.h"