diff --git a/wadsrc/static/shaders/glsl/gammacorrection.fp b/wadsrc/static/shaders/glsl/gammacorrection.fp
index 1deb1a600..fe40ac680 100644
--- a/wadsrc/static/shaders/glsl/gammacorrection.fp
+++ b/wadsrc/static/shaders/glsl/gammacorrection.fp
@@ -3,6 +3,8 @@ uniform sampler2D tex;
 in vec4 vTexCoord;
 in vec4 vColor;
 
+out vec4 FragColor;
+
 void main()
 {
 	vec3 color = texture(tex, vTexCoord.st).rgb;