diff --git a/res/shaders/simple.frag b/res/shaders/simple.frag
index f40b7fd..68218c5 100644
--- a/res/shaders/simple.frag
+++ b/res/shaders/simple.frag
@@ -45,7 +45,7 @@ float dither(vec2 uv) {
 void main()
 {
     // only sample normals for normal mapped geometry
-    vec3 normal = bool(normalMapped) ? vec3(texture(normalSampler, textureCoordinates)) : normal_in;
+    vec3 normal = bool(normalMapped) ? 2*vec3(texture(normalSampler, textureCoordinates))-1 : normal_in;
 
     vec3 N = normalize(normal);
     vec3 V = normalize(cameraPosition - worldPosition);