diff --git a/src/libutil/fs-sink.cc b/src/libutil/fs-sink.cc
index 154346cee..b1e342c77 100644
--- a/src/libutil/fs-sink.cc
+++ b/src/libutil/fs-sink.cc
@@ -71,7 +71,8 @@ static GlobalConfig::Register r1(&restoreSinkSettings);
 
 void RestoreSink::createDirectory(const CanonPath & path)
 {
-    std::filesystem::create_directory(dstPath / path.rel());
+    if (!std::filesystem::create_directory(dstPath / path.rel()))
+        throw Error("path '%s' already exists", (dstPath / path.rel()).string());
 };
 
 struct RestoreRegularFile : CreateRegularFileSink {
diff --git a/tests/functional/nars.sh b/tests/functional/nars.sh
index c58d12cd5..106bd10fc 100755
--- a/tests/functional/nars.sh
+++ b/tests/functional/nars.sh
@@ -10,6 +10,9 @@ clearStore
 rm -rf "$TEST_ROOT/out"
 expectStderr 1 nix-store --restore "$TEST_ROOT/out" < duplicate.nar | grepQuiet "NAR directory is not sorted"
 
+# Check that nix-store --restore fails if the output already exists.
+expectStderr 1 nix-store --restore "$TEST_ROOT/out" < duplicate.nar | grepQuiet "path '.*/out/' already exists"
+
 # Check whether restoring and dumping a NAR that contains case
 # collisions is round-tripping, even on a case-insensitive system.
 rm -rf "$TEST_ROOT/case"