diff --git a/cabal-testsuite/cabal-testsuite.cabal b/cabal-testsuite/cabal-testsuite.cabal
index 1a6ed19967c..1c27e40c23c 100644
--- a/cabal-testsuite/cabal-testsuite.cabal
+++ b/cabal-testsuite/cabal-testsuite.cabal
@@ -91,7 +91,7 @@ executable cabal-tests
   import: shared
   main-is: cabal-tests.hs
   hs-source-dirs: main
-  ghc-options: -threaded
+  ghc-options: -threaded -rtsopts
   -- Make sure these are built before the executable is run
   build-tool-depends: cabal-testsuite:test-runtime-deps
   build-depends:
diff --git a/validate.sh b/validate.sh
index 3b56a945c84..40ad0576b5f 100755
--- a/validate.sh
+++ b/validate.sh
@@ -324,6 +324,13 @@ CABAL_TESTSUITE_BDIR="$(pwd)/$BUILDDIR/build/$ARCH/$BASEHC/cabal-testsuite-3"
 CABALNEWBUILD="${CABAL} build $JOBS -w $HC --builddir=$BUILDDIR --project-file=$PROJECTFILE"
 CABALLISTBIN="${CABAL} list-bin --builddir=$BUILDDIR --project-file=$PROJECTFILE"
 
+# This was needed in some local Windows MSYS2 environments
+# but breaks CI for Windows + GHC 9.0.2, thus it is set only on non-CI executions
+# of validate.sh
+# https://github.com/haskell/cabal/issues/9571
+# https://github.com/haskell/cabal/pull/10114
+RTSOPTS="$([[ $ARCH = "x86_64-windows" && -z "$CI" ]] && echo "+RTS --io-manager=native" || echo "")"
+
 # header
 #######################################################################
 
@@ -344,6 +351,7 @@ doctest:             $DOCTEST
 benchmarks:          $BENCHMARKS
 verbose:             $VERBOSE
 extra compilers:     $EXTRAHCS
+extra RTS options:   $RTSOPTS
 
 EOF
 }
@@ -426,7 +434,7 @@ fi
 step_lib_suite() {
 print_header "Cabal: cabal-testsuite"
 
-CMD="$($CABALLISTBIN cabal-testsuite:exe:cabal-tests) --builddir=$CABAL_TESTSUITE_BDIR $TESTSUITEJOBS --with-ghc=$HC --hide-successes"
+CMD="$($CABALLISTBIN cabal-testsuite:exe:cabal-tests) --builddir=$CABAL_TESTSUITE_BDIR $TESTSUITEJOBS --with-ghc=$HC --hide-successes $RTSOPTS"
 (cd cabal-testsuite && timed $CMD) || exit 1
 }
 
@@ -468,7 +476,7 @@ CMD="$($CABALLISTBIN cabal-install:test:integration-tests2) -j1 --hide-successes
 step_cli_suite() {
 print_header "cabal-install: cabal-testsuite"
 
-CMD="$($CABALLISTBIN cabal-testsuite:exe:cabal-tests) --builddir=$CABAL_TESTSUITE_BDIR --with-cabal=$($CABALLISTBIN cabal-install:exe:cabal) $TESTSUITEJOBS  --with-ghc=$HC --hide-successes --intree-cabal-lib=$PWD --test-tmp=$PWD/testdb"
+CMD="$($CABALLISTBIN cabal-testsuite:exe:cabal-tests) --builddir=$CABAL_TESTSUITE_BDIR --with-cabal=$($CABALLISTBIN cabal-install:exe:cabal) $TESTSUITEJOBS  --with-ghc=$HC --hide-successes --intree-cabal-lib=$PWD --test-tmp=$PWD/testdb $RTSOPTS"
 (cd cabal-testsuite && timed $CMD) || exit 1
 }