diff --git a/test/algorithms/set_operations/union/test_union.hpp b/test/algorithms/set_operations/union/test_union.hpp
index d8ce75da8..b9bc63e65 100644
--- a/test/algorithms/set_operations/union/test_union.hpp
+++ b/test/algorithms/set_operations/union/test_union.hpp
@@ -55,6 +55,20 @@ struct ut_settings
 
 };
 
+#if defined(BOOST_GEOMETRY_TEST_CHECK_VALID_INPUT)
+template <typename Geometry>
+inline void check_input_validity(std::string const& caseid, int case_index,
+                Geometry const& geometry)
+{
+    std::string message;
+    if (!bg::is_valid(geometry, message))
+    {
+        std::cout << caseid << " Input ["
+                  << case_index << "] not valid" << std::endl
+                  << "   ("  << message << ")" << std::endl;
+    }
+}
+#endif
 
 template <typename OutputType, typename G1, typename G2>
 void test_union(std::string const& caseid, G1 const& g1, G2 const& g2,
@@ -73,6 +87,11 @@ void test_union(std::string const& caseid, G1 const& g1, G2 const& g2,
     std::cout << "*** UNION " << caseid << std::endl;
 #endif
 
+#if defined(BOOST_GEOMETRY_TEST_CHECK_VALID_INPUT)
+    check_input_validity(caseid, 0, g1);
+    check_input_validity(caseid, 1, g2);
+#endif
+
     bg::union_(g1, g2, clip);
 
     typename bg::default_area_result<OutputType>::type area = 0;