diff --git a/src/libstore/gc.cc b/src/libstore/gc.cc
index 6cd7efbc9..9ef8972f3 100644
--- a/src/libstore/gc.cc
+++ b/src/libstore/gc.cc
@@ -622,9 +622,8 @@ void LocalStore::collectGarbage(const GCOptions & options, GCResults & results)
         /* There may be temp directories in the store that are still in use
            by another process. We need to be sure that we can acquire an
            exclusive lock before deleting them. */
-        AutoCloseFD tmpDirFd;
-        if (baseName.rfind("add-", 0) == 0) {
-            tmpDirFd = open(realPath.c_str(), O_RDONLY | O_DIRECTORY);
+        if (baseName.find("tmp-", 0) == 0) {
+            AutoCloseFD tmpDirFd = open(realPath.c_str(), O_RDONLY | O_DIRECTORY);
             if (tmpDirFd.get() == -1 || !lockFile(tmpDirFd.get(), ltWrite, false)) {
                 debug("skipping locked tempdir '%s'", realPath);
                 return;
diff --git a/src/libstore/local-store.cc b/src/libstore/local-store.cc
index 5ee451da3..0b07cde34 100644
--- a/src/libstore/local-store.cc
+++ b/src/libstore/local-store.cc
@@ -1433,7 +1433,6 @@ StorePath LocalStore::addToStoreFromDump(Source & source0, std::string_view name
             } else {
                 /* Move the temporary path we restored above. */
                 moveFile(tempPath, realPath);
-                tempDirFd.close();
             }
 
             /* For computing the nar hash. In recursive SHA-256 mode, this
@@ -1520,7 +1519,7 @@ std::pair<Path, AutoCloseFD> LocalStore::createTempDirInStore()
         /* There is a slight possibility that `tmpDir' gets deleted by
            the GC between createTempDir() and when we acquire a lock on it.
            We'll repeat until 'tmpDir' exists and we've locked it. */
-        tmpDirFn = createTempDir(realStoreDir, "add");
+        tmpDirFn = createTempDir(realStoreDir, "tmp");
         tmpDirFd = open(tmpDirFn.c_str(), O_RDONLY | O_DIRECTORY);
         if (tmpDirFd.get() < 0) {
             continue;