diff --git a/source/glbackend/glbackend.cpp b/source/glbackend/glbackend.cpp
index 6a84e5b7e..2332a67be 100644
--- a/source/glbackend/glbackend.cpp
+++ b/source/glbackend/glbackend.cpp
@@ -262,6 +262,7 @@ void PolymostRenderState::Apply(FRenderState& state, GLState& oldState)
 	FVector4 blendcol(0, 0, 0, 0);
 	int flags = 0;
 
+	if (Flags & RF_ShadeInterpolate) flags |= 16384;	// hijack a free bit in here.
 	if (fullscreenTint != 0xffffff) flags |= 16;
 	if (hictint_flags != -1)
 	{
@@ -283,8 +284,8 @@ void PolymostRenderState::Apply(FRenderState& state, GLState& oldState)
 			blendcol = modcol;	// WTF???, but the tinting code really uses the same color for both!
 			flags |= (((hictint_flags & TINTF_BLENDMASK) >> 6) + 1) & TextureManipulation::BlendMask;
 		}
-		addcol.W = flags;
 	}
+	addcol.W = flags;
 	state.SetTextureColors(&modcol.X, &addcol.X, &blendcol.X);
 
 	if (matrixIndex[Matrix_Model] != -1)
diff --git a/wadsrc/static/shaders/glsl/func_paletted.fp b/wadsrc/static/shaders/glsl/func_paletted.fp
index 1be496917..a9a4cca86 100644
--- a/wadsrc/static/shaders/glsl/func_paletted.fp
+++ b/wadsrc/static/shaders/glsl/func_paletted.fp
@@ -9,7 +9,7 @@ const int RF_ShadeInterpolate = 64;
 
 vec4 ProcessTexel()
 {
-	int u_flags = RF_ShadeInterpolate;
+	int blendflags = int(uTextureAddColor.a);
 	float fullbright = 0.0;
 	vec4 color;
 	float coordX = vTexCoord.x;
@@ -30,7 +30,7 @@ vec4 ProcessTexel()
 
 	color = texture(tex, newCoord);
 
-	float visibility = max(uGlobVis * uLightFactor * z - ((u_flags & RF_ShadeInterpolate) != 0.0? 0.5 : 0.0), 0.0);
+	float visibility = max(uGlobVis * uLightFactor * z - ((blendflags & 16384) != 0? 0.5 : 0.0), 0.0);
 	float numShades = float(uPalLightLevels & 255);
 	float shade = (1.0 - uLightLevel) * (numShades);
 	shade = clamp((shade + visibility), 0.0, numShades - 1.0);
@@ -41,7 +41,7 @@ vec4 ProcessTexel()
 	int colorIndex = int(colorIndexF * 255.0 + 0.1); // The 0.1 is for roundoff error compensation.
 	vec4 palettedColor = texelFetch(texture2, ivec2(colorIndex, 0), 0);
 	
-	if ((u_flags & RF_ShadeInterpolate) != 0)
+	if ((blendflags & 16384) != 0)
 	{
 		// Get the next shaded palette index for interpolation
 		colorIndexF = texelFetch(texture3, ivec2(palindex, shadeindex+1), 0).r;
diff --git a/wadsrc/static/shaders/glsl/main.fp b/wadsrc/static/shaders/glsl/main.fp
index 95b01abf2..d12d8affd 100644
--- a/wadsrc/static/shaders/glsl/main.fp
+++ b/wadsrc/static/shaders/glsl/main.fp
@@ -203,7 +203,7 @@ vec4 getTexel(vec2 st)
 	
 	// Apply the texture modification colors.
 	int blendflags = int(uTextureAddColor.a);	// this alpha is unused otherwise
-	if (blendflags != 0)	
+	if ((blendflags &  0x3fff) != 0)			// keep the upper flags for other things.
 	{
 		// only apply the texture manipulation if it contains something.
 		texel = ApplyTextureManipulation(texel, blendflags);