diff --git a/tests/overlay-local-store/add-lower-inner.sh b/tests/overlay-local-store/add-lower-inner.sh
index 40a1f397c..8c71f0780 100755
--- a/tests/overlay-local-store/add-lower-inner.sh
+++ b/tests/overlay-local-store/add-lower-inner.sh
@@ -18,14 +18,14 @@ mountOverlayfs
 
 # Add something to the overlay store
 overlayPath=$(addTextToStore "$storeB" "overlay-file" "Add to overlay store")
-stat "$TEST_ROOT/merged-store/$overlayPath"
+stat "$storeVolume/merged-store/$overlayPath"
 
 # Now add something to the lower store
 lowerPath=$(addTextToStore "$storeA" "lower-file" "Add to lower store")
-stat "$TEST_ROOT/store-a/$lowerPath"
+stat "$storeVolume/store-a/$lowerPath"
 
 # Remount overlayfs to ensure synchronization
-mount -o remount "$TEST_ROOT/merged-store/nix/store"
+mount -o remount "$storeVolume/merged-store/nix/store"
 
 # Path should be accessible via overlay store
-stat "$TEST_ROOT/merged-store/$lowerPath"
+stat "$storeVolume/merged-store/$lowerPath"
diff --git a/tests/overlay-local-store/bad-uris.sh b/tests/overlay-local-store/bad-uris.sh
index d4261bd97..c59264735 100644
--- a/tests/overlay-local-store/bad-uris.sh
+++ b/tests/overlay-local-store/bad-uris.sh
@@ -7,8 +7,8 @@ storeDirs
 mkdir -p $TEST_ROOT/bad_test
 badTestRoot=$TEST_ROOT/bad_test
 storeBadRoot="local-overlay?root=$badTestRoot&lower-store=$storeA&upper-layer=$storeBTop"
-storeBadLower="local-overlay?root=$TEST_ROOT/merged-store&lower-store=$badTestRoot&upper-layer=$storeBTop"
-storeBadUpper="local-overlay?root=$TEST_ROOT/merged-store&lower-store=$storeA&upper-layer=$badTestRoot"
+storeBadLower="local-overlay?root=$storeVolume/merged-store&lower-store=$badTestRoot&upper-layer=$storeBTop"
+storeBadUpper="local-overlay?root=$storeVolume/merged-store&lower-store=$storeA&upper-layer=$badTestRoot"
 
 declare -a storesBad=(
     "$storeBadRoot" "$storeBadLower" "$storeBadUpper"
diff --git a/tests/overlay-local-store/check-post-init-inner.sh b/tests/overlay-local-store/check-post-init-inner.sh
index 37ed8c113..c7d1c70d4 100755
--- a/tests/overlay-local-store/check-post-init-inner.sh
+++ b/tests/overlay-local-store/check-post-init-inner.sh
@@ -25,7 +25,7 @@ stat $(toRealPath "$storeA/nix/store" "$path")
 expect 1 stat $(toRealPath "$storeBTop" "$path")
 
 # Checking for path in overlay store matching lower layer
-diff $(toRealPath "$storeA/nix/store" "$path") $(toRealPath "$TEST_ROOT/merged-store/nix/store" "$path")
+diff $(toRealPath "$storeA/nix/store" "$path") $(toRealPath "$storeVolume/merged-store/nix/store" "$path")
 
 # Checking requisites query agreement
 [[ \
diff --git a/tests/overlay-local-store/common.sh b/tests/overlay-local-store/common.sh
index 6aec96ba1..686523e9c 100644
--- a/tests/overlay-local-store/common.sh
+++ b/tests/overlay-local-store/common.sh
@@ -12,30 +12,36 @@ setupConfig () {
   echo "build-users-group = " >> "$NIX_CONF_DIR"/nix.conf
 }
 
+
+
 storeDirs () {
-  storesRoot="$TEST_ROOT/stores"
-  mkdir -p "$storesRoot"
-  mount -t tmpfs tmpfs "$storesRoot"
-  storeA="$storesRoot/store-a"
-  storeBTop="$storesRoot/store-b"
-  storeB="local-overlay?root=$storesRoot/merged-store&lower-store=$storeA&upper-layer=$storeBTop"
+  # Attempt to create store dirs on tmpfs volume.
+  # This ensures lowerdir, upperdir and workdir will be on
+  # a consistent filesystem that fully supports OverlayFS.
+  storeVolume="$TEST_ROOT/stores"
+  mkdir -p "$storeVolume"
+  mount -t tmpfs tmpfs "$storeVolume" || true  # But continue anyway if that fails.
+
+  storeA="$storeVolume/store-a"
+  storeBTop="$storeVolume/store-b"
+  storeB="local-overlay?root=$storeVolume/merged-store&lower-store=$storeA&upper-layer=$storeBTop"
   # Creating testing directories
-  mkdir -p "$storesRoot"/{store-a/nix/store,store-b,merged-store/nix/store,workdir}
+  mkdir -p "$storeVolume"/{store-a/nix/store,store-b,merged-store/nix/store,workdir}
 }
 
 # Mounting Overlay Store
 mountOverlayfs () {
-  mergedStorePath="$storesRoot/merged-store/nix/store"
+  mergedStorePath="$storeVolume/merged-store/nix/store"
   mount -t overlay overlay \
     -o lowerdir="$storeA/nix/store" \
     -o upperdir="$storeBTop" \
-    -o workdir="$storesRoot/workdir" \
+    -o workdir="$storeVolume/workdir" \
     "$mergedStorePath" \
     || skipTest "overlayfs is not supported"
 
   cleanupOverlay () {
-    umount "$storesRoot/merged-store/nix/store"
-    rm -r $storesRoot/workdir
+    umount "$storeVolume/merged-store/nix/store"
+    rm -r $storeVolume/workdir
   }
   trap cleanupOverlay EXIT
 }
diff --git a/tests/overlay-local-store/optimise-inner.sh b/tests/overlay-local-store/optimise-inner.sh
index 079e22326..2b778b311 100755
--- a/tests/overlay-local-store/optimise-inner.sh
+++ b/tests/overlay-local-store/optimise-inner.sh
@@ -17,7 +17,7 @@ initLowerStore
 mountOverlayfs
 
 # Create a file to add to store
-dupFilePath="$storesRoot/dup-file"
+dupFilePath="$TEST_ROOT/dup-file"
 echo Duplicate > "$dupFilePath"
 
 # Add it to the overlay store (it will be written to the upper layer)