diff --git a/public/xash3d_mathlib.c b/public/xash3d_mathlib.c
index 082d5ca2..e1610580 100644
--- a/public/xash3d_mathlib.c
+++ b/public/xash3d_mathlib.c
@@ -144,7 +144,7 @@ void RoundUpHullSize( vec3_t size )
 rsqrt
 =================
 */
-float rsqrt( float number )
+float Q_rsqrt( float number )
 {
 	int	i;
 	float	x, y;
diff --git a/public/xash3d_mathlib.h b/public/xash3d_mathlib.h
index 98ac4164..c9413699 100644
--- a/public/xash3d_mathlib.h
+++ b/public/xash3d_mathlib.h
@@ -119,7 +119,7 @@ CONSTANTS AND HELPER MACROS
 #define VectorLerp( v1, lerp, v2, c ) ((c)[0] = (v1)[0] + (lerp) * ((v2)[0] - (v1)[0]), (c)[1] = (v1)[1] + (lerp) * ((v2)[1] - (v1)[1]), (c)[2] = (v1)[2] + (lerp) * ((v2)[2] - (v1)[2]))
 #define VectorNormalize( v ) { float ilength = (float)sqrt(DotProduct(v, v));if (ilength) ilength = 1.0f / ilength;v[0] *= ilength;v[1] *= ilength;v[2] *= ilength; }
 #define VectorNormalize2( v, dest ) {float ilength = (float)sqrt(DotProduct(v,v));if (ilength) ilength = 1.0f / ilength;dest[0] = v[0] * ilength;dest[1] = v[1] * ilength;dest[2] = v[2] * ilength; }
-#define VectorNormalizeFast( v ) {float	ilength = (float)rsqrt(DotProduct(v,v)); v[0] *= ilength; v[1] *= ilength; v[2] *= ilength; }
+#define VectorNormalizeFast( v ) {float ilength = (float)Q_rsqrt(DotProduct(v,v)); v[0] *= ilength; v[1] *= ilength; v[2] *= ilength; }
 #define VectorNormalizeLength( v ) VectorNormalizeLength2((v), (v))
 #define VectorNegate(x, y) ((y)[0] = -(x)[0], (y)[1] = -(x)[1], (y)[2] = -(x)[2])
 #define VectorM(scale1, b1, c) ((c)[0] = (scale1) * (b1)[0],(c)[1] = (scale1) * (b1)[1],(c)[2] = (scale1) * (b1)[2])
@@ -158,7 +158,7 @@ typedef struct mplane_s mplane_t;
 typedef struct mstudiobone_s mstudiobone_t;
 typedef struct mstudioanim_s mstudioanim_t;
 
-float rsqrt( float number );
+float Q_rsqrt( float number );
 uint16_t FloatToHalf( float v );
 float HalfToFloat( uint16_t h );
 void RoundUpHullSize( vec3_t size );