diff --git a/ref/gl/gl_frustum.c b/ref/gl/gl_frustum.c
index 3a25913d..38db4f4d 100644
--- a/ref/gl/gl_frustum.c
+++ b/ref/gl/gl_frustum.c
@@ -16,7 +16,7 @@ GNU General Public License for more details.
 #include "gl_local.h"
 #include "xash3d_mathlib.h"
 
-void GL_FrustumSetPlane( gl_frustum_t *out, int side, const vec3_t vecNormal, float flDist )
+static void GL_FrustumSetPlane( gl_frustum_t *out, int side, const vec3_t vecNormal, float flDist )
 {
 	Assert( side >= 0 && side < FRUSTUM_PLANES );
 
diff --git a/ref/gl/gl_frustum.h b/ref/gl/gl_frustum.h
index 520ebff8..fcf36f0b 100644
--- a/ref/gl/gl_frustum.h
+++ b/ref/gl/gl_frustum.h
@@ -33,7 +33,6 @@ typedef struct gl_frustum_s
 
 void GL_FrustumInitProj( gl_frustum_t *out, float flZNear, float flZFar, float flFovX, float flFovY );
 void GL_FrustumInitOrtho( gl_frustum_t *out, float xLeft, float xRight, float yTop, float yBottom, float flZNear, float flZFar );
-void GL_FrustumSetPlane( gl_frustum_t *out, int side, const vec3_t vecNormal, float flDist );
 
 // cull methods
 qboolean GL_FrustumCullBox( gl_frustum_t *out, const vec3_t mins, const vec3_t maxs, int userClipFlags );