diff --git a/sc2/src/sc2code/libs/graphics/cmap.c b/sc2/src/sc2code/libs/graphics/cmap.c
index 13e509cbc..731304b27 100644
--- a/sc2/src/sc2code/libs/graphics/cmap.c
+++ b/sc2/src/sc2code/libs/graphics/cmap.c
@@ -428,7 +428,7 @@ finish_colormap_xform (int which)
  * Only one thread should ever be allowed to be calling this at any time
  */
 BOOLEAN
-XFormColorMap_step ()
+XFormColorMap_step (void)
 {
 	BOOLEAN Changed = FALSE;
 	int x;
diff --git a/sc2/src/sc2code/libs/graphics/cmap.h b/sc2/src/sc2code/libs/graphics/cmap.h
index 09dd857f9..6faabd3dd 100644
--- a/sc2/src/sc2code/libs/graphics/cmap.h
+++ b/sc2/src/sc2code/libs/graphics/cmap.h
@@ -56,7 +56,7 @@ extern void TFB_ColorMapToRGB (TFB_Palette *pal, int colormap_index);
 extern TFB_ColorMap * TFB_GetColorMap (int index);
 extern void TFB_ReturnColorMap (TFB_ColorMap *map);
 
-extern BOOLEAN XFormColorMap_step ();
+extern BOOLEAN XFormColorMap_step (void);
 
 
 #endif