diff --git a/wadsrc/static/shaders/glsl/main.fp b/wadsrc/static/shaders/glsl/main.fp
index 1bf583b06..41150fa20 100644
--- a/wadsrc/static/shaders/glsl/main.fp
+++ b/wadsrc/static/shaders/glsl/main.fp
@@ -73,7 +73,7 @@ vec4 getTexel(vec2 st)
 			break;
 			
 		case 4:	// TM_REDTOALPHA
-			texel = vec4(1.0, 1.0, 1.0, texel.r);
+			texel = vec4(1.0, 1.0, 1.0, texel.r*texel.a);
 			break;
 			
 		case 5:	// TM_CLAMPY