diff --git a/dev-haskell/stm/stm-2.5.0.1-r1.ebuild b/dev-haskell/stm/stm-2.5.0.1-r1.ebuild
index fe9afffd95d7e..8119160c28999 100644
--- a/dev-haskell/stm/stm-2.5.0.1-r1.ebuild
+++ b/dev-haskell/stm/stm-2.5.0.1-r1.ebuild
@@ -21,7 +21,7 @@ CABAL_CHDEPS=(
 )
 
 RDEPEND="
-	>=dev-lang/ghc-8.10.6:=
+	>=dev-lang/ghc-8.10.6:= <dev-lang/ghc-9.1
 "
 DEPEND="${RDEPEND}
 	>=dev-haskell/cabal-2.2.0.1