diff --git a/src/libfetchers/fetch-to-store.cc b/src/libfetchers/fetch-to-store.cc
index 65aa72a6c36a..f7f4aed4d8d3 100644
--- a/src/libfetchers/fetch-to-store.cc
+++ b/src/libfetchers/fetch-to-store.cc
@@ -15,6 +15,17 @@ StorePath fetchToStore(
 {
     // FIXME: add an optimisation for the case where the accessor is
     // a `PosixSourceAccessor` pointing to a store path.
+    if (store.isInStore(path.path.abs()) && !filter) {
+        auto storePath = store.toStorePath(path.path.abs());
+        if (storePath.second == "") {
+            debug(
+                "source path '%s' is already in the store: '%s', '%s'",
+                path,
+                store.printStorePath(storePath.first),
+                storePath.second);
+            return storePath.first;
+        }
+    }
 
     std::optional<fetchers::Cache::Key> cacheKey;
 
diff --git a/tests/functional/flakes/flakes.sh b/tests/functional/flakes/flakes.sh
index 26b91eda751a..461a3c2e4a29 100755
--- a/tests/functional/flakes/flakes.sh
+++ b/tests/functional/flakes/flakes.sh
@@ -246,11 +246,6 @@ nix build -o "$TEST_ROOT/result" --expr "(builtins.getFlake \"git+file://$flake1
 # Regression test for baseNameOf on the root of the flake.
 [[ $(nix eval --raw flake1#baseName) =~ ^[a-z0-9]+-source$ ]]
 
-# Test that the root of a tree returns a path named /nix/store/<hash1>-<hash2>-source.
-# This behavior is *not* desired, but has existed for a while.
-# Issue #10627 what to do about it.
-[[ $(nix eval --raw flake1#root) =~ ^.*/[a-z0-9]+-[a-z0-9]+-source$ ]]
-
 # Building a flake with an unlocked dependency should fail in pure mode.
 (! nix build -o "$TEST_ROOT/result" flake2#bar --no-registries)
 (! nix build -o "$TEST_ROOT/result" flake2#bar --no-use-registries)