diff --git a/common/polylib.c b/common/polylib.c
index f4fc4f35..ee247f30 100644
--- a/common/polylib.c
+++ b/common/polylib.c
@@ -240,7 +240,7 @@ CopyWinding(const winding_t * w)
  * =============
  */
 void
-ClipWinding(const winding_t * in, vec3_t normal, vec_t dist,
+ClipWinding(const winding_t * in, const vec3_t normal, vec_t dist,
             winding_t ** front, winding_t ** back)
 {
     vec_t dists[MAX_POINTS_ON_WINDING + 4];
diff --git a/include/common/polylib.h b/include/common/polylib.h
index ebb2a56b..bd8425bd 100644
--- a/include/common/polylib.h
+++ b/include/common/polylib.h
@@ -27,7 +27,7 @@ winding_t *AllocWinding(int points);
 vec_t WindingArea(const winding_t * w);
 void WindingCenter(const winding_t * w, vec3_t center);
 void WindingBounds (const winding_t *w, vec3_t mins, vec3_t maxs);
-void ClipWinding(const winding_t * in, vec3_t normal, vec_t dist,
+void ClipWinding(const winding_t * in, const vec3_t normal, vec_t dist,
                  winding_t ** front, winding_t ** back);
 winding_t *ChopWinding(winding_t * in, vec3_t normal, vec_t dist);
 winding_t *CopyWinding(const winding_t * w);