diff --git a/src/blackmisc/simulation/simulatorinfo.cpp b/src/blackmisc/simulation/simulatorinfo.cpp
index 7b4188dca..00ecb369b 100644
--- a/src/blackmisc/simulation/simulatorinfo.cpp
+++ b/src/blackmisc/simulation/simulatorinfo.cpp
@@ -181,10 +181,15 @@ namespace BlackMisc
             return CValueObject::toIcon();
         }
 
-        void CSimulatorInfo::add(const CSimulatorInfo &other)
+        CSimulatorInfo CSimulatorInfo::add(const CSimulatorInfo &other)
         {
-            if (other.isUnspecified()) { return; }
+            // anything to add?
+            if (other.isUnspecified())   { return None; }
+            if (this->matchesAll(other)) { return None; }
+
             this->setSimulator(this->getSimulator() | other.getSimulator());
+            const CSimulatorInfo delta(this->getSimulator() & other.getSimulator());
+            return delta;
         }
 
         QSet<CSimulatorInfo> CSimulatorInfo::asSingleSimulatorSet() const
diff --git a/src/blackmisc/simulation/simulatorinfo.h b/src/blackmisc/simulation/simulatorinfo.h
index 31af5cb07..7b8ab071c 100644
--- a/src/blackmisc/simulation/simulatorinfo.h
+++ b/src/blackmisc/simulation/simulatorinfo.h
@@ -157,7 +157,7 @@ namespace BlackMisc
             CIcon toIcon() const;
 
             //! Add simulator
-            void add(const CSimulatorInfo &other);
+            CSimulatorInfo add(const CSimulatorInfo &other);
 
             //! As a set of single simulator info objects
             QSet<CSimulatorInfo> asSingleSimulatorSet() const;