diff --git a/src/blackmisc/simulation/interpolationrenderingsetup.cpp b/src/blackmisc/simulation/interpolationrenderingsetup.cpp
index fc582e9cf..e32306b2d 100644
--- a/src/blackmisc/simulation/interpolationrenderingsetup.cpp
+++ b/src/blackmisc/simulation/interpolationrenderingsetup.cpp
@@ -322,5 +322,11 @@ namespace BlackMisc
             }
             CInterpolationAndRenderingSetupBase::setPropertyByIndex(index, variant);
         }
+
+        const CInterpolationAndRenderingSetupPerCallsign &CInterpolationAndRenderingSetupPerCallsign::null()
+        {
+            static const CInterpolationAndRenderingSetupPerCallsign null;
+            return null;
+        }
     } // ns
 } // ns
diff --git a/src/blackmisc/simulation/interpolationrenderingsetup.h b/src/blackmisc/simulation/interpolationrenderingsetup.h
index 9e9d74e94..3f40bbe1e 100644
--- a/src/blackmisc/simulation/interpolationrenderingsetup.h
+++ b/src/blackmisc/simulation/interpolationrenderingsetup.h
@@ -219,12 +219,18 @@ namespace BlackMisc
             //! Set callsign
             void setCallsign(const Aviation::CCallsign &callsign) { m_callsign = callsign; }
 
+            //! NULL?
+            bool isNull() const { return m_callsign.isEmpty(); }
+
             //! \copydoc BlackMisc::Mixin::Index::propertyByIndex
             CVariant propertyByIndex(const CPropertyIndex &index) const;
 
             //! \copydoc BlackMisc::Mixin::Index::setPropertyByIndex
             void setPropertyByIndex(const CPropertyIndex &index, const CVariant &variant);
 
+            //! NULL object
+            static const CInterpolationAndRenderingSetupPerCallsign &null();
+
         private:
             Aviation::CCallsign m_callsign;
 
diff --git a/src/blackmisc/simulation/interpolationsetupprovider.cpp b/src/blackmisc/simulation/interpolationsetupprovider.cpp
index bb580621f..2501926ef 100644
--- a/src/blackmisc/simulation/interpolationsetupprovider.cpp
+++ b/src/blackmisc/simulation/interpolationsetupprovider.cpp
@@ -18,7 +18,8 @@ namespace BlackMisc
         CInterpolationAndRenderingSetupPerCallsign IInterpolationSetupProvider::getInterpolationSetupPerCallsignOrDefault(const CCallsign &callsign) const
         {
             QReadLocker l(&m_lockSetup);
-            return m_setups.contains(callsign) ? m_setups.value(callsign) : CInterpolationAndRenderingSetupPerCallsign(callsign, m_globalSetup);
+            if (!m_setups.contains(callsign)) { return CInterpolationAndRenderingSetupPerCallsign(callsign, m_globalSetup); }
+            return m_setups.value(callsign);
         }
 
         CInterpolationSetupList IInterpolationSetupProvider::getInterpolationSetupsPerCallsign() const