diff --git a/osc/util/ar.py b/osc/util/ar.py
index 66c02918b..8c501e66c 100644
--- a/osc/util/ar.py
+++ b/osc/util/ar.py
@@ -147,8 +147,10 @@ def _fixupFilenames(self):
         """
 
         # read extended header with long file names and then only seek into the right offsets
-        self.__file.seek(self.ext_fnhdr.dataoff, os.SEEK_SET)
-        ext_fnhdr_data = self.__file.read(self.ext_fnhdr.size)
+        ext_fnhdr_data = None
+        if self.ext_fnhdr:
+            self.__file.seek(self.ext_fnhdr.dataoff, os.SEEK_SET)
+            ext_fnhdr_data = self.__file.read(self.ext_fnhdr.size)
 
         for h in self.hdrs:
             if h.file == b'/':
@@ -159,8 +161,12 @@ def _fixupFilenames(self):
                 h.file = h.file[:-1]
                 continue
 
+            if not h.file.startswith(b'/'):
+                continue
+
             # long file name
             assert h.file[0:1] == b"/"
+            assert ext_fnhdr_data is not None
             start = int(h.file[1:])
             end = ext_fnhdr_data.find(b'/', start)
 
diff --git a/tests/fixtures/README b/tests/fixtures/README
index 2b7fa007f..2801ea7ef 100644
--- a/tests/fixtures/README
+++ b/tests/fixtures/README
@@ -33,3 +33,9 @@ Create archive.cpio
 
 printf "/tmp/foo\0/123\0very-long-long-long-long-name\0very-long-long-long-long-name2\0very-long-name
 -with-newline\0a\nb\0dir/file\0" | cpio -ocv0 --owner=root:root > archive.cpio
+
+
+Create archive-no-ext_fnhdr.ar
+------------------------------
+
+ar qP archive-no-ext_fnhdr.ar dir/file
diff --git a/tests/fixtures/archive-no-ext_fnhdr.ar b/tests/fixtures/archive-no-ext_fnhdr.ar
new file mode 100644
index 000000000..1da64b1bc
--- /dev/null
+++ b/tests/fixtures/archive-no-ext_fnhdr.ar
@@ -0,0 +1,3 @@
+!<arch>
+dir/file/       1724142481  1000  1000  100644  14        `
+file-in-a-dir
diff --git a/tests/test_util_ar.py b/tests/test_util_ar.py
index 227fd4737..099e7b4d1 100644
--- a/tests/test_util_ar.py
+++ b/tests/test_util_ar.py
@@ -81,6 +81,12 @@ def test_saveTo_abspath(self):
         # this is supposed to throw an error, extracting files with absolute paths might overwrite system files
         self.assertRaises(ArError, f.saveTo, self.tmpdir)
 
+    def test_no_exthdr(self):
+        self.archive = os.path.join(FIXTURES_DIR, "archive-no-ext_fnhdr.ar")
+        self.ar = Ar(self.archive)
+        self.ar.read()
+        self.test_saveTo_subdir()
+
 
 if __name__ == "__main__":
     unittest.main()