diff --git a/include/QF/mathlib.h b/include/QF/mathlib.h
index bdade22a5..f6978ef50 100644
--- a/include/QF/mathlib.h
+++ b/include/QF/mathlib.h
@@ -632,6 +632,7 @@ void Mat4Transpose (const mat4_t a, mat4_t b);
 int Mat4Inverse (const mat4_t a, mat4_t b);
 void Mat4Mult (const mat4_t a, const mat4_t b, mat4_t c);
 void Mat4MultVec (const mat4_t a, const vec3_t b, vec3_t c);
+void Mat4as3MultVec (const mat4_t a, const vec3_t b, vec3_t c);
 /** Decompose a column major matrix into its component transformations.
 
 	This gives the matrix's rotation as a quaternion, shear, scale
diff --git a/libs/util/mathlib.c b/libs/util/mathlib.c
index 0c4428702..d5876b268 100644
--- a/libs/util/mathlib.c
+++ b/libs/util/mathlib.c
@@ -920,6 +920,17 @@ Mat4MultVec (const mat4_t a, const vec3_t b, vec3_t c)
 		c[i] = a[i + 0] * tb[0] + a[i + 4] * b[1] + a[i + 8] * b[2] + a[i +12];
 }
 
+void
+Mat4as3MultVec (const mat4_t a, const vec3_t b, vec3_t c)
+{
+	int         i;
+	vec3_t      tb;
+
+	VectorCopy (b, tb);
+	for (i = 0; i < 3; i++)
+		c[i] = a[i + 0] * tb[0] + a[i + 4] * b[1] + a[i + 8] * b[2];
+}
+
 int
 Mat4Decompose (const mat4_t mat, quat_t rot, vec3_t shear, vec3_t scale,
 			   vec3_t trans)