diff --git a/sys/powerpc/include/cpufunc.h b/sys/powerpc/include/cpufunc.h
index bb01fdbada06..c949d53d0481 100644
--- a/sys/powerpc/include/cpufunc.h
+++ b/sys/powerpc/include/cpufunc.h
@@ -166,21 +166,21 @@ static __inline void
 eieio(void)
 {
 
-	__asm __volatile ("eieio");
+	__asm __volatile ("eieio" : : : "memory");
 }
 
 static __inline void
 isync(void)
 {
 
-	__asm __volatile ("isync");
+	__asm __volatile ("isync" : : : "memory");
 }
 
 static __inline void
 powerpc_sync(void)
 {
 
-	__asm __volatile ("sync");
+	__asm __volatile ("sync" : : : "memory");
 }
 
 static __inline register_t