diff --git a/src/renderers/shaders/ShaderChunk/metalnessmap_fragment.glsl b/src/renderers/shaders/ShaderChunk/metalnessmap_fragment.glsl
index d0e719015916ca1183a8a111040b8220e9089b29..be8f3694c752f497921bbf5ff3ff285bf8e8ef0c 100644
--- a/src/renderers/shaders/ShaderChunk/metalnessmap_fragment.glsl
+++ b/src/renderers/shaders/ShaderChunk/metalnessmap_fragment.glsl
@@ -3,6 +3,6 @@ float metalnessFactor = metalness;
 #ifdef USE_METALNESSMAP
 
 	vec4 texelMetalness = texture2D( metalnessMap, vUv );
-	metalnessFactor = texelMetalness.r; // note equality, not *=
+	metalnessFactor *= texelMetalness.r;
 
 #endif