diff --git a/bundles/org.openhab.core/src/test/java/org/openhab/core/library/types/QuantityTypeToInvertibleUnitTest.java b/bundles/org.openhab.core/src/test/java/org/openhab/core/library/types/QuantityTypeToInvertibleUnitTest.java
index dd6a1fe2d..3f60bec48 100644
--- a/bundles/org.openhab.core/src/test/java/org/openhab/core/library/types/QuantityTypeToInvertibleUnitTest.java
+++ b/bundles/org.openhab.core/src/test/java/org/openhab/core/library/types/QuantityTypeToInvertibleUnitTest.java
@@ -125,6 +125,11 @@ class QuantityTypeToInvertibleUnitTest {
 
         assertEquals(0.1, v1.doubleValue(), 0.01);
         assertEquals(10, v2.doubleValue(), 0.01);
+
+        // fail cases
+        assertNull(v1.toInvertibleUnit(SIUnits.METRE));
+        assertNull(v2.toInvertibleUnit(SIUnits.METRE));
+        assertNull(QuantityType.valueOf(5, Units.HERTZ).toInvertibleUnit(SIUnits.METRE));
     }
 
     /**