diff --git a/external/resinsight/LibCore/cvfVector4.inl b/external/resinsight/LibCore/cvfVector4.inl
index d505d0cfc..cc944d6f3 100644
--- a/external/resinsight/LibCore/cvfVector4.inl
+++ b/external/resinsight/LibCore/cvfVector4.inl
@@ -491,7 +491,7 @@ inline void Vector4<S>::setZero()
 template<typename S>
 inline bool Vector4<S>::isZero() const
 {
-    return (m_v[0] == 0) && (m_v[1] == 0) && (m_v[2] == 0) && (m_v[2] == 0);
+    return (m_v[0] == 0) && (m_v[1] == 0) && (m_v[2] == 0) && (m_v[3] == 0);
 }