diff --git a/src/ShellCheck/Checks/ShellSupport.hs b/src/ShellCheck/Checks/ShellSupport.hs
index de5f78c..054661a 100644
--- a/src/ShellCheck/Checks/ShellSupport.hs
+++ b/src/ShellCheck/Checks/ShellSupport.hs
@@ -391,11 +391,10 @@ checkBashisms = ForShell [Sh, Dash] $ \t -> do
             ("unset", Just ["f", "v"]),
             ("wait", Just [])
             ]
-    bashism t@(T_SourceCommand id src _) =
-        let name = fromMaybe "" $ getCommandName src
-        in when (name == "source") $ warnMsg id "'source' in place of '.' is"
-    bashism (TA_Expansion _ (T_Literal id str : _)) | str `matches` radix =
-        when (str `matches` radix) $ warnMsg id "arithmetic base conversion is"
+    bashism t@(T_SourceCommand id src _)
+        | getCommandName src == Just "source" = warnMsg id "'source' in place of '.' is"
+    bashism (TA_Expansion _ (T_Literal id str : _))
+        | str `matches` radix = warnMsg id "arithmetic base conversion is"
       where
         radix = mkRegex "^[0-9]+#"
     bashism _ = return ()