--- mathlib/mathlib_base.cpp
+++ mathlib/mathlib_base.cpp
@@ -1653,19 +1653,19 @@ void MatrixCopy( const matrix3x4_t& in, matrix3x4_t& out )
 	memcpy( out.Base(), in.Base(), sizeof( float ) * 3 * 4 );
 }
 
 void MatrixInvert( const matrix3x4_t& in, matrix3x4_t& out )
 {
 	Assert( s_bMathlibInitialized );
 	if ( &in == &out )
 	{
-		V_swap(out[0][1],out[1][0]);
-		V_swap(out[0][2],out[2][0]);
-		V_swap(out[1][2],out[2][1]);
+		V_swap(out[0][1],out[1][0]);
+		V_swap(out[0][2],out[2][0]);
+		V_swap(out[1][2],out[2][1]);
 	}
 	else
 	{
 		// I'm guessing this only works on a 3x4 orthonormal matrix
 		out[0][0] = in[0][0];
 		out[0][1] = in[1][0];
 		out[0][2] = in[2][0];