Index: source/blender/gpu/shaders/gpu_shader_material.glsl
===================================================================
--- source/blender/gpu/shaders/gpu_shader_material.glsl	(revision 57656)
+++ source/blender/gpu/shaders/gpu_shader_material.glsl	(working copy)
@@ -812,7 +812,10 @@
 void shade_norm(vec3 normal, out vec3 outnormal)
 {
 	/* blender render normal is negated */
-	outnormal = -normalize(normal);
+	if(gl_FrontFacing){
+        outnormal = -normalize(normal);}
+    else{
+        outnormal = normalize(normal);}
 }
 
 void mtex_rgb_blend(vec3 outcol, vec3 texcol, float fact, float facg, out vec3 incol)
@@ -1412,7 +1415,10 @@
 	vec3 B = tangent.w * cross(normal, tangent.xyz);
 
 	outnormal = texnormal.x*tangent.xyz + texnormal.y*B + texnormal.z*normal;
-	outnormal = normalize(outnormal);
+	if(gl_FrontFacing){
+        outnormal = normalize(outnormal);}
+    else{
+        outnormal = -normalize(outnormal);}
 }
 
 void mtex_blend_normal(float norfac, vec3 normal, vec3 newnormal, out vec3 outnormal)