diff --git a/test/variant_eq_ne.cpp b/test/variant_eq_ne.cpp
index b2fc19d..87e2ecb 100644
--- a/test/variant_eq_ne.cpp
+++ b/test/variant_eq_ne.cpp
@@ -88,5 +88,12 @@ int main()
         BOOST_TEST_NOT( v1 != v2 );
     }
 
+    {
+        variant<monostate> v1, v2;
+
+        BOOST_TEST( v1 == v2 );
+        BOOST_TEST_NOT( v1 != v2 );
+    }
+
     return boost::report_errors();
 }
diff --git a/test/variant_eq_ne_cx.cpp b/test/variant_eq_ne_cx.cpp
index 9ebb751..bfd90c2 100644
--- a/test/variant_eq_ne_cx.cpp
+++ b/test/variant_eq_ne_cx.cpp
@@ -93,6 +93,13 @@ int main()
         STATIC_ASSERT( !(v1 == v2) );
         STATIC_ASSERT( !(v1 != v2) );
     }
+
+    {
+        constexpr variant<monostate> v1, v2;
+
+        STATIC_ASSERT( v1 == v2 );
+        STATIC_ASSERT( !(v1 != v2) );
+    }
 }
 
 #endif
diff --git a/test/variant_lt_gt.cpp b/test/variant_lt_gt.cpp
index 688209f..f2a931f 100644
--- a/test/variant_lt_gt.cpp
+++ b/test/variant_lt_gt.cpp
@@ -81,5 +81,14 @@ int main()
         BOOST_TEST_NOT( v1 >= v2 );
     }
 
+    {
+        variant<monostate> v1, v2;
+
+        BOOST_TEST_NOT( v1 < v2 );
+        BOOST_TEST_NOT( v1 > v2 );
+        BOOST_TEST( v1 <= v2 );
+        BOOST_TEST( v1 >= v2 );
+    }
+
     return boost::report_errors();
 }
diff --git a/test/variant_lt_gt_cx.cpp b/test/variant_lt_gt_cx.cpp
index b570846..6d1dfc9 100644
--- a/test/variant_lt_gt_cx.cpp
+++ b/test/variant_lt_gt_cx.cpp
@@ -86,6 +86,15 @@ int main()
         STATIC_ASSERT( !(v1 <= v2) );
         STATIC_ASSERT( !(v1 >= v2) );
     }
+
+    {
+        constexpr variant<monostate> v1, v2;
+
+        STATIC_ASSERT( !(v1 < v2) );
+        STATIC_ASSERT( !(v1 > v2) );
+        STATIC_ASSERT( v1 <= v2 );
+        STATIC_ASSERT( v1 >= v2 );
+    }
 }
 
 #endif