diff --git a/src/blackmisc/pq/physicalquantity.cpp b/src/blackmisc/pq/physicalquantity.cpp
index 764646cdf..65009227a 100644
--- a/src/blackmisc/pq/physicalquantity.cpp
+++ b/src/blackmisc/pq/physicalquantity.cpp
@@ -222,7 +222,10 @@ namespace BlackMisc
         bool CPhysicalQuantity<MU, PQ>::lessThan(const CPhysicalQuantity<MU, PQ> &other) const
         {
             if (*this == other) return false;
-            if (this->isNull() || other.isNull()) return false;
+
+            if (isNull() < other.isNull()) { return true; }
+            if (isNull() > other.isNull()) { return false; }
+            if (isNull() && other.isNull()) { return false; }
 
             return (m_value < other.value(m_unit));
         }
diff --git a/tests/blackmisc/pq/testphysicalquantities/testphysicalquantities.cpp b/tests/blackmisc/pq/testphysicalquantities/testphysicalquantities.cpp
index c350faaa4..7fd415003 100644
--- a/tests/blackmisc/pq/testphysicalquantities/testphysicalquantities.cpp
+++ b/tests/blackmisc/pq/testphysicalquantities/testphysicalquantities.cpp
@@ -96,6 +96,14 @@ namespace BlackMiscTest
 
         CFrequencyUnit fu1 = CFrequencyUnit::Hz();
         QVERIFY2(fu1 != du1, "Hz must not be meter");
+
+        // null comparisons
+        const CLength null(CLength::null());
+        const CLength nonNull(1, CLengthUnit::m());
+        QVERIFY2(null == CLength::null(), "null is equal to null");
+        QVERIFY2(!(null < CLength::null()), "null is equivalent to null");
+        QVERIFY2(null != nonNull, "null is not equal to non-null");
+        QVERIFY2((null < nonNull) != (null > nonNull), "null is ordered wrt non-null");
     }
 
     void CTestPhysicalQuantities::lengthBasics()
diff --git a/tests/blackmisc/testvariantandmap/testvariantandmap.cpp b/tests/blackmisc/testvariantandmap/testvariantandmap.cpp
index 52a740395..e55cdba4f 100644
--- a/tests/blackmisc/testvariantandmap/testvariantandmap.cpp
+++ b/tests/blackmisc/testvariantandmap/testvariantandmap.cpp
@@ -85,9 +85,8 @@ namespace BlackMiscTest
         CLength l4(-1, CLengthUnit::m());
         QVERIFY2(l1 != l3, "Null length and non-null length should not be equal");
         QVERIFY2(l1 != l4, "Null length and non-null length should not be equal");
-        QVERIFY2(!(l1 < l4), "Null length and non-null length should not be comparable");
-        QVERIFY2(!(l1 > l4), "Null length and non-null length should not be comparable");
-        QVERIFY2(compare(l1, l4) < 0, "Null length and non-null length should be sortable");
+        QVERIFY2((l1 < l4) != (l1 > l4), "Null length and non-null length should be comparable");
+        QVERIFY2(compare(l1, l4) != 0, "Null length and non-null length should be sortable");
 
         CVariant station1qv = CVariant::fromValue(station1);
         QVERIFY2(station1 == station1, "Station should be equal");