diff --git a/src/plugin/ecfmp/AircraftFlowMeasureMap.cpp b/src/plugin/ecfmp/AircraftFlowMeasureMap.cpp
index a92c9b25..f01327ca 100644
--- a/src/plugin/ecfmp/AircraftFlowMeasureMap.cpp
+++ b/src/plugin/ecfmp/AircraftFlowMeasureMap.cpp
@@ -58,6 +58,9 @@ namespace UKControllerPlugin::ECFMP {
             // Add the flow measure to the map by id
             flowMeasureIdMap.emplace(measure->Id(), measure);
 
+            // Initialise the flow measure's callsign map
+            flowMeasureCallsignMap.emplace(measure, std::unordered_set<std::string>());
+
             // Check each of the flightplans and see if it applies to them
             plugin.ApplyFunctionToAllFlightplans([&measure, this](
                                                      const Euroscope::EuroScopeCFlightPlanInterface& flightplan,
diff --git a/test/plugin/ecfmp/AircraftFlowMeasureMapTest.cpp b/test/plugin/ecfmp/AircraftFlowMeasureMapTest.cpp
index 9496550a..cfab2c51 100644
--- a/test/plugin/ecfmp/AircraftFlowMeasureMapTest.cpp
+++ b/test/plugin/ecfmp/AircraftFlowMeasureMapTest.cpp
@@ -125,6 +125,30 @@ namespace UKControllerPluginTest::ECFMP {
         EXPECT_EQ(0, map.GetFlowMeasuresForCallsign("BAW456").size());
     }
 
+    TEST_F(AircraftFlowMeasureMapTest, FlowMeasuresWithdrawingHandlesNoCallsignsAssociatedWithMeasure)
+    {
+        // Flightplan 1 will be applicable to the measure, flightplan 2, not so
+        EXPECT_CALL(*mockFlowMeasure1, ApplicableToAircraft(testing::_, testing::_))
+            .WillRepeatedly(testing::Return(false));
+
+        EXPECT_CALL(*mockFlowMeasure2, ApplicableToAircraft(testing::_, testing::_))
+            .WillRepeatedly(testing::Return(false));
+
+        map.OnEvent(::ECFMP::Plugin::FlowMeasureActivatedEvent{mockFlowMeasure1});
+        map.OnEvent(::ECFMP::Plugin::FlowMeasureActivatedEvent{mockFlowMeasure2});
+
+        EXPECT_EQ(0, map.GetFlowMeasuresForCallsign("BAW123").size());
+        EXPECT_EQ(0, map.GetFlowMeasuresForCallsign("BAW456").size());
+
+        // Withdraw the measures
+        EXPECT_NO_THROW(map.OnEvent(::ECFMP::Plugin::FlowMeasureWithdrawnEvent{mockFlowMeasure1}));
+        EXPECT_NO_THROW(map.OnEvent(::ECFMP::Plugin::FlowMeasureWithdrawnEvent{mockFlowMeasure2}));
+
+        // Check that flightplan 1 now has just the second measure, but flightplan 2 has only the second
+        EXPECT_EQ(0, map.GetFlowMeasuresForCallsign("BAW123").size());
+        EXPECT_EQ(0, map.GetFlowMeasuresForCallsign("BAW456").size());
+    }
+
     TEST_F(AircraftFlowMeasureMapTest, FlowMeasuresExpiringRemoveThemFromAircraftsActiveFlowMeasures)
     {
         // Flightplan 1 will be applicable to the measure, flightplan 2, not so
@@ -186,6 +210,30 @@ namespace UKControllerPluginTest::ECFMP {
         EXPECT_EQ(0, map.GetFlowMeasuresForCallsign("BAW456").size());
     }
 
+    TEST_F(AircraftFlowMeasureMapTest, FlowMeasuresExpiringHandlesNoCallsignsAssociatedWithMeasure)
+    {
+        // Flightplan 1 will be applicable to the measure, flightplan 2, not so
+        EXPECT_CALL(*mockFlowMeasure1, ApplicableToAircraft(testing::_, testing::_))
+            .WillRepeatedly(testing::Return(false));
+
+        EXPECT_CALL(*mockFlowMeasure2, ApplicableToAircraft(testing::_, testing::_))
+            .WillRepeatedly(testing::Return(false));
+
+        map.OnEvent(::ECFMP::Plugin::FlowMeasureActivatedEvent{mockFlowMeasure1});
+        map.OnEvent(::ECFMP::Plugin::FlowMeasureActivatedEvent{mockFlowMeasure2});
+
+        EXPECT_EQ(0, map.GetFlowMeasuresForCallsign("BAW123").size());
+        EXPECT_EQ(0, map.GetFlowMeasuresForCallsign("BAW456").size());
+
+        // Withdraw the measures
+        EXPECT_NO_THROW(map.OnEvent(::ECFMP::Plugin::FlowMeasureExpiredEvent{mockFlowMeasure1}));
+        EXPECT_NO_THROW(map.OnEvent(::ECFMP::Plugin::FlowMeasureExpiredEvent{mockFlowMeasure2}));
+
+        // Check that flightplan 1 now has just the second measure, but flightplan 2 has only the second
+        EXPECT_EQ(0, map.GetFlowMeasuresForCallsign("BAW123").size());
+        EXPECT_EQ(0, map.GetFlowMeasuresForCallsign("BAW456").size());
+    }
+
     TEST_F(AircraftFlowMeasureMapTest, FlightplansDisconnectingRemoveTheirActiveFlowMeasures)
     {
         // Flightplan 1 will be applicable to the measure, flightplan 2, not so