diff --git a/include/common/bspfile.hh b/include/common/bspfile.hh
index 62d96015..5357d32f 100644
--- a/include/common/bspfile.hh
+++ b/include/common/bspfile.hh
@@ -339,6 +339,8 @@ typedef struct {
 #define TEX_MINLIGHT_COLOR_B_SHIFT      36
 #define TEX_MINLIGHT_COLOR_B_MASK       (255ULL << TEX_MINLIGHT_COLOR_B_SHIFT)    /* 8 bit value, blue minlight color for this face. */
 #define TEX_NOSHADOW  (1ULL << 44)   /* don't cast a shadow */
+#define TEX_PHONG_ANGLE_CONCAVE_SHIFT   45
+#define TEX_PHONG_ANGLE_CONCAVE_MASK    (255ULL << TEX_PHONG_ANGLE_CONCAVE_SHIFT) /* 8 bit value. if non zero, overrides _phong_angle for concave joints. */
 
 // Q2 Texture flags.
 #define    Q2_SURF_LIGHT      0x1        // value will hold the light strength
diff --git a/include/qbsp/qbsp.hh b/include/qbsp/qbsp.hh
index 4b85f751..31c97eea 100644
--- a/include/qbsp/qbsp.hh
+++ b/include/qbsp/qbsp.hh
@@ -134,8 +134,9 @@
 #define TEX_MINLIGHT_COLOR_G_MASK       (255ULL << TEX_MINLIGHT_COLOR_G_SHIFT)    /* 8 bit value, green minlight color for this face. */
 #define TEX_MINLIGHT_COLOR_B_SHIFT      36
 #define TEX_MINLIGHT_COLOR_B_MASK       (255ULL << TEX_MINLIGHT_COLOR_B_SHIFT)    /* 8 bit value, blue minlight color for this face. */
-
 #define TEX_NOSHADOW  (1ULL << 44)   /* don't cast a shadow */
+#define TEX_PHONG_ANGLE_CONCAVE_SHIFT   45
+#define TEX_PHONG_ANGLE_CONCAVE_MASK    (255ULL << TEX_PHONG_ANGLE_CONCAVE_SHIFT) /* 8 bit value. if non zero, overrides _phong_angle for concave joints. */
 
 /*
  * The quality of the bsp output is highly sensitive to these epsilon values.
diff --git a/qbsp/map.cc b/qbsp/map.cc
index 56b6c517..569853ae 100644
--- a/qbsp/map.cc
+++ b/qbsp/map.cc
@@ -295,7 +295,7 @@ FindTexinfoEnt(mtexinfo_t *texinfo, const mapentity_t *entity)
         }
     }
     
-    // handle "_phong" and "_phong_angle"
+    // handle "_phong" and "_phong_angle" and "_phong_angle_concave"
     vec_t phongangle = atof(ValueForKey(entity, "_phong_angle"));
     const int phong = atoi(ValueForKey(entity, "_phong"));
     
@@ -304,10 +304,16 @@ FindTexinfoEnt(mtexinfo_t *texinfo, const mapentity_t *entity)
     }
     
     if (phongangle) {
-        const uint8_t phongangle_byte = (uint8_t) qmax(0, qmin(255, (int)rint(phongangle)));
+        const uint64_t phongangle_byte = (uint64_t) qmax(0, qmin(255, (int)rint(phongangle)));
         flags |= (phongangle_byte << TEX_PHONG_ANGLE_SHIFT);
     }
     
+    const vec_t phong_angle_concave = atof(ValueForKey(entity, "_phong_angle_concave"));
+    {
+        const uint64_t phong_angle_concave_byte = (uint64_t) qmax(0, qmin(255, (int)rint(phong_angle_concave)));
+        flags |= (phong_angle_concave_byte << TEX_PHONG_ANGLE_CONCAVE_SHIFT);
+    }
+    
     // handle "_minlight"
     const vec_t minlight = atof(ValueForKey(entity, "_minlight"));
     if (minlight > 0) {