diff --git a/polymer/eduke32/build/include/sdlayer.h b/polymer/eduke32/build/include/sdlayer.h
index b09eee231..3afd83567 100644
--- a/polymer/eduke32/build/include/sdlayer.h
+++ b/polymer/eduke32/build/include/sdlayer.h
@@ -10,7 +10,7 @@
 struct sdlappicon {
 	int32_t width,height;
 	uint32_t *pixels;
-	char *mask;
+	unsigned char *mask;
 };
 
 #else