diff -ur a/include/assimp/pbrmaterial.h b/include/assimp/pbrmaterial.h
--- a/include/assimp/pbrmaterial.h	2022-02-03 21:09:18.050000000 +0000
+++ b/include/assimp/pbrmaterial.h	2022-02-03 21:09:44.930000000 +0000
@@ -61,7 +61,7 @@
 #define AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_METALLIC_FACTOR AI_MATKEY_METALLIC_FACTOR
 #define AI_MATKEY_GLTF_PBRMETALLICROUGHNESS_ROUGHNESS_FACTOR AI_MATKEY_ROUGHNESS_FACTOR
 
-//#define AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS "$mat.gltf.pbrSpecularGlossiness", 0, 0
+#define AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS "$mat.gltf.pbrSpecularGlossiness", 0, 0
 #define AI_MATKEY_GLTF_PBRSPECULARGLOSSINESS_GLOSSINESS_FACTOR AI_MATKEY_GLOSSINESS_FACTOR
 
 // Use AI_MATKEY_SHADING_MODEL == aiShadingMode_Unlit instead