diff --git a/.github/workflows/oldest.yml b/.github/workflows/oldest.yml
index b2fa85a6e..c73311ae0 100644
--- a/.github/workflows/oldest.yml
+++ b/.github/workflows/oldest.yml
@@ -21,7 +21,7 @@ jobs:
       # XXX supposed to be interpolated by $ghc below, but this is not working
       ghc: 8107
       # stack config for this ghc:
-      stack: stack --stack-yaml=stack8.10.yaml
+      stack: stack --stack-yaml=stack810.yaml
 
     steps:
 
diff --git a/stack8.10.yaml b/stack810.yaml
similarity index 100%
rename from stack8.10.yaml
rename to stack810.yaml
diff --git a/stack9.0.yaml b/stack90.yaml
similarity index 100%
rename from stack9.0.yaml
rename to stack90.yaml
diff --git a/stack9.12.yaml b/stack912.yaml
similarity index 100%
rename from stack9.12.yaml
rename to stack912.yaml
diff --git a/stack9.2.yaml b/stack92.yaml
similarity index 100%
rename from stack9.2.yaml
rename to stack92.yaml
diff --git a/stack9.4.yaml b/stack94.yaml
similarity index 100%
rename from stack9.4.yaml
rename to stack94.yaml
diff --git a/stack9.6.yaml b/stack96.yaml
similarity index 100%
rename from stack9.6.yaml
rename to stack96.yaml
diff --git a/stack9.8.yaml b/stack98.yaml
similarity index 100%
rename from stack9.8.yaml
rename to stack98.yaml