diff --git a/Eigen/src/Core/Diagonal.h b/Eigen/src/Core/Diagonal.h
index a3bd071b5..654cfc9d0 100644
--- a/Eigen/src/Core/Diagonal.h
+++ b/Eigen/src/Core/Diagonal.h
@@ -91,8 +91,12 @@ class Diagonal : public internal::dense_xpr_base<Diagonal<MatrixType, DiagIndex_
 
   typedef std::conditional_t<internal::is_lvalue<MatrixType>::value, Scalar, const Scalar> ScalarWithConstIfNotLvalue;
 
-  EIGEN_DEVICE_FUNC inline ScalarWithConstIfNotLvalue* data() { return &(m_matrix.coeffRef(rowOffset(), colOffset())); }
-  EIGEN_DEVICE_FUNC inline const Scalar* data() const { return &(m_matrix.coeffRef(rowOffset(), colOffset())); }
+  EIGEN_DEVICE_FUNC inline ScalarWithConstIfNotLvalue* data() {
+    return rows() > 0 ? &(m_matrix.coeffRef(rowOffset(), colOffset())) : nullptr;
+  }
+  EIGEN_DEVICE_FUNC inline const Scalar* data() const {
+    return rows() > 0 ? &(m_matrix.coeffRef(rowOffset(), colOffset())) : nullptr;
+  }
 
   EIGEN_DEVICE_FUNC inline Scalar& coeffRef(Index row, Index) {
     EIGEN_STATIC_ASSERT_LVALUE(MatrixType)
diff --git a/test/array_cwise.cpp b/test/array_cwise.cpp
index f361cce77..086f48ff1 100644
--- a/test/array_cwise.cpp
+++ b/test/array_cwise.cpp
@@ -773,6 +773,7 @@ void comparisons(const ArrayType& m) {
 
   // test bug2966: select did not support some scalar types that forbade implicit conversions from bool
   ArrayX<scalar_wrapper> m5(10);
+  m5.setConstant(scalar_wrapper(0));
   m5 = (m5 == scalar_wrapper(0)).select(m5, m5);
 }