diff --git a/wadsrc/static/shaders/glsl/main.fp b/wadsrc/static/shaders/glsl/main.fp
index 0c55adb50..145f76964 100644
--- a/wadsrc/static/shaders/glsl/main.fp
+++ b/wadsrc/static/shaders/glsl/main.fp
@@ -123,7 +123,7 @@ float R_DoomLightingEquation(float light)
 	float shade = 64.0 - (L + 12.0) * 32.0/128.0;
 	float lightscale;
 	if (uPalLightLevels != 0)
-		lightscale = clamp(int(shade - min(24.0, vis)) / 32.0, 0.0, 31.0/32.0);
+		lightscale = clamp(float(int(shade - min(24.0, vis))) / 32.0, 0.0, 31.0/32.0);
 	else
 		lightscale = clamp((shade - min(24.0, vis)) / 32.0, 0.0, 31.0/32.0);