diff --git a/src/App/Program.fs b/src/App/Program.fs
index e8fb0560..3ffad782 100644
--- a/src/App/Program.fs
+++ b/src/App/Program.fs
@@ -754,9 +754,26 @@ let main argv =
                 { LogDebugPartitions = List.ofSeq mission.LogDebugPartitions
                   LogTracePartitions = List.ofSeq mission.LogTracePartitions }
 
+            let looksLikeFlagValue (s: string) =
+                match s.ToLowerInvariant() with
+                | "true" | "false" -> true
+                | _ ->
+                    let (isNumeric, _) = System.Double.TryParse(s)
+                    isNumeric
+
             match Seq.tryFind (allMissions.ContainsKey >> not) mission.Missions with
             | Some e ->
                 (LogError "Unknown mission: %s" e
+
+                 if looksLikeFlagValue e then
+                     LogError
+                         "Note: '%s' looks like a value for a command-line flag rather than a mission name. You may have passed an argument to a flag that doesn't accept one (e.g. --catchup-skip-known-results-for-testing=false instead of --catchup-skip-known-results-for-testing)."
+                         e
+                 elif e.StartsWith("-") then
+                     LogError
+                         "Note: '%s' looks like a command-line option rather than a mission name. You may have a typo in the option name, or used an option not supported by the 'mission' verb."
+                         e
+
                  LogError "Available missions:"
                  Map.iter (fun k _ -> LogError "        %s" k) allMissions
                  1)