diff --git a/Eigen/src/Geometry/AngleAxis.h b/Eigen/src/Geometry/AngleAxis.h
index 0af3c1b08..83ee1be46 100644
--- a/Eigen/src/Geometry/AngleAxis.h
+++ b/Eigen/src/Geometry/AngleAxis.h
@@ -178,7 +178,7 @@ EIGEN_DEVICE_FUNC AngleAxis<Scalar>& AngleAxis<Scalar>::operator=(const Quaterni
   if (n != Scalar(0))
   {
     m_angle = Scalar(2)*atan2(n, abs(q.w()));
-    if(q.w() < 0)
+    if(q.w() < Scalar(0))
       n = -n;
     m_axis  = q.vec() / n;
   }