diff --git a/idlib/geometry/Surface_Polytope.cpp b/idlib/geometry/Surface_Polytope.cpp
index 87a344c..3fc91d6 100644
--- a/idlib/geometry/Surface_Polytope.cpp
+++ b/idlib/geometry/Surface_Polytope.cpp
@@ -62,7 +62,7 @@ void idSurface_Polytope::FromPlanes( const idPlane *planes, const int numPlanes
 		}
 
 		for ( j = 0; j < w.GetNumPoints(); j++ ) {
-			for ( k = 0; k < verts.Num(); j++ ) {
+			for ( k = 0; k < verts.Num(); k++ ) {
 				if ( verts[k].xyz.Compare( w[j].ToVec3(), POLYTOPE_VERTEX_EPSILON ) ) {
 					break;
 				}
diff --git a/idlib/math/Matrix.cpp b/idlib/math/Matrix.cpp
index b013764..f723ee9 100644
--- a/idlib/math/Matrix.cpp
+++ b/idlib/math/Matrix.cpp
@@ -3125,9 +3125,9 @@ bool idMatX::IsOrthonormal( const float epsilon ) const {
 
 		ptr2 = mat + i;
 		sum = ptr2[0] * ptr2[0] - 1.0f;
-		for ( i = 1; i < numRows; i++ ) {
+		for ( int j = 1; j < numRows; j++ ) {
 			ptr2 += numColumns;
-			sum += ptr2[i] * ptr2[i];
+			sum += ptr2[i] * ptr2[j];
 		}
 		if ( idMath::Fabs( sum ) > epsilon ) {
 			return false;