diff --git a/tests/overlay-local-store/optimise-inner.sh b/tests/overlay-local-store/optimise-inner.sh
index 2b778b311..b7994054c 100755
--- a/tests/overlay-local-store/optimise-inner.sh
+++ b/tests/overlay-local-store/optimise-inner.sh
@@ -32,7 +32,7 @@ remountOverlayfs
 dupFilename="${dupFileStorePath#/nix/store}"
 lowerPath="$storeA/$dupFileStorePath"
 upperPath="$storeBTop/$dupFilename"
-overlayPath="$mergedStorePath/$dupFilename"
+overlayPath="$storeBRoot/nix/store/$dupFilename"
 
 # Check store path exists in both layers and overlay
 lowerInode=$(stat -c %i "$lowerPath")