diff --git a/src/Shaders/Flat.frag b/src/Shaders/Flat.frag
index 665ed51d6..2cd2453e7 100644
--- a/src/Shaders/Flat.frag
+++ b/src/Shaders/Flat.frag
@@ -25,6 +25,7 @@
 #ifndef NEW_GLSL
 #define fragmentColor gl_FragColor
 #define texture texture2D
+#define in varying
 #endif
 
 #ifdef TEXTURED