diff --git a/compiler/iface/FlagChecker.hs b/compiler/iface/FlagChecker.hs
index 611228e5673dad4d89ca1787e86d30cdf09ba2e6..5e4a7092bfa6a724d0daf2aa458d2d086de9a3f3 100644
--- a/compiler/iface/FlagChecker.hs
+++ b/compiler/iface/FlagChecker.hs
@@ -41,7 +41,9 @@ fingerprintDynFlags DynFlags{..} nameio =
         -- -i, -osuf, -hcsuf, -hisuf, -odir, -hidir, -stubdir, -o, -ohi
         paths = (map normalise importPaths,
                    [ objectSuf, hcSuf, hiSuf ],
-                   [ objectDir, hiDir, stubDir, outputFile, outputHi ])
+                   [ objectDir, hiDir, stubDir, outputHi ])
+                   -- NB. not outputFile, we don't want "ghc --make M -o <file>"
+                   -- to force recompilation when <file> changes.
 
         -- -fprof-auto etc.
         prof = if opt_SccProfilingOn then fromEnum profAuto else 0