diff --git a/src/engine/qcommon/q_math.cpp b/src/engine/qcommon/q_math.cpp
index b7b7a78add..4fe267702d 100644
--- a/src/engine/qcommon/q_math.cpp
+++ b/src/engine/qcommon/q_math.cpp
@@ -2871,7 +2871,7 @@ void QuatFromMatrix( quat_t q, const matrix_t m )
 
 	if ( t > 0.0f )
 	{
-		s = ( 1.0f / sqrtf( t ) ) * 0.5f;
+		s = Q_rsqrt( t ) * 0.5f;
 
 		q[ 3 ] = s * t;
 		q[ 2 ] = ( m[ 1 ] - m[ 4 ] ) * s;
@@ -2882,7 +2882,7 @@ void QuatFromMatrix( quat_t q, const matrix_t m )
 	else if ( m[ 0 ] > m[ 5 ] && m[ 0 ] > m[ 10 ] )
 	{
 		t = m[ 0 ] - m[ 5 ] - m[ 10 ] + 1.0f;
-		s = ( 1.0f / sqrtf( t ) ) * 0.5f;
+		s = Q_rsqrt( t ) * 0.5f;
 
 		q[ 0 ] = s * t;
 		q[ 1 ] = ( m[ 1 ] + m[ 4 ] ) * s;
@@ -2893,7 +2893,7 @@ void QuatFromMatrix( quat_t q, const matrix_t m )
 	else if ( m[ 5 ] > m[ 10 ] )
 	{
 		t = -m[ 0 ] + m[ 5 ] - m[ 10 ] + 1.0f;
-		s = ( 1.0f / sqrtf( t ) ) * 0.5f;
+		s = Q_rsqrt( t ) * 0.5f;
 
 		q[ 1 ] = s * t;
 		q[ 0 ] = ( m[ 1 ] + m[ 4 ] ) * s;
@@ -2904,7 +2904,7 @@ void QuatFromMatrix( quat_t q, const matrix_t m )
 	else
 	{
 		t = -m[ 0 ] - m[ 5 ] + m[ 10 ] + 1.0f;
-		s = ( 1.0f / sqrtf( t ) ) * 0.5f;
+		s = Q_rsqrt( t ) * 0.5f;
 
 		q[ 2 ] = s * t;
 		q[ 3 ] = ( m[ 1 ] - m[ 4 ] ) * s;