diff --git a/testsuite/driver/testlib.py b/testsuite/driver/testlib.py
index 06c7889fb83eba28a32903e1b626d2753aa27941..98e84e1e545f2e715a1b1ac0826cd5c1eede1934 100644
--- a/testsuite/driver/testlib.py
+++ b/testsuite/driver/testlib.py
@@ -2620,9 +2620,6 @@ def normalise_errmsg(s: str) -> str:
     # Same thing for .jsexe directories generated by the JS backend
     s = re.sub('([^\\s])\\.jsexe', '\\1', s)
 
-    # normalise slashes, minimise Windows/Unix filename differences
-    s = re.sub('\\\\', '/', s)
-
     # hpc executable is given ghc suffix
     s = re.sub('hpc-ghc', 'hpc', s)