diff --git a/hledger-lib/Hledger/Read/CsvReader.hs b/hledger-lib/Hledger/Read/CsvReader.hs
index 20dd0234a..4545a1e2a 100644
--- a/hledger-lib/Hledger/Read/CsvReader.hs
+++ b/hledger-lib/Hledger/Read/CsvReader.hs
@@ -183,7 +183,7 @@ maxFieldIndex r = maximumDef (-1) $ catMaybes [
 -- rulesFileFor CliOpts{rules_file_=Just f} _ = f
 -- rulesFileFor CliOpts{rules_file_=Nothing} csvfile = replaceExtension csvfile ".rules"
 rulesFileFor :: FilePath -> FilePath
-rulesFileFor = flip replaceExtension ".rules"
+rulesFileFor = (++ ".rules")
 
 newRulesFileContent :: String
 newRulesFileContent = let prognameandversion = "hledger" in