diff --git a/kojihub/kojihub.py b/kojihub/kojihub.py
index 69d6eaf5..c848bc99 100644
--- a/kojihub/kojihub.py
+++ b/kojihub/kojihub.py
@@ -8273,7 +8273,7 @@ def add_rpm_sig(an_rpm, sighdr, sigkey=None):
     if not os.path.isdir(builddir):
         raise koji.GenericError("No such directory: %s" % builddir)
     if sigkey is not None:
-        verify_name_internal(sigkey)
+        validate_sigkey_value(sigkey)
 
     # verify sigmd5 matches rpm and pick sigkey if needed
     rawhdr = koji.RawHeader(sighdr)
@@ -8324,10 +8324,25 @@ def add_rpm_sig(an_rpm, sighdr, sigkey=None):
                               sigkey=sigkey, sighash=sighash, build=binfo, rpm=rinfo)
 
 
+def validate_sigkey_value(sigkey):
+    convert_value(sigkey, cast=str, check_only=True)
+    if sigkey == '':
+        # special case for the unsigned sig header
+        return
+    if '/' in sigkey or sigkey.startswith('.'):
+        # not allowed because the value is used in a path
+        raise koji.GenericError("Invalid sigkey value")
+    if sigkey != sigkey.lower():
+        # we require lowercase because koji has historically forced lowercase for this value
+        # e.g. in query_rpm_sigs
+        raise koji.GenericError("Invalid sigkey value. Must be lowercase")
+    verify_name_internal(sigkey)
+
+
 def rename_rpm_sig(rpminfo, oldkey, newkey):
     """Change the sigkey for an rpm signature"""
 
-    verify_name_internal(newkey)
+    validate_sigkey_value(newkey)
     rinfo = get_rpm(rpminfo, strict=True)
     nvra = "%(name)s-%(version)s-%(release)s.%(arch)s" % rinfo
     if rinfo['external_repo_id']:
diff --git a/tests/test_hub/test_add_rpm_sig.py b/tests/test_hub/test_add_rpm_sig.py
index 3505d3d4..c40067ae 100644
--- a/tests/test_hub/test_add_rpm_sig.py
+++ b/tests/test_hub/test_add_rpm_sig.py
@@ -146,15 +146,23 @@ class TestAddRPMSig(unittest.TestCase):
     def test_add_rpm_sig_bad_sigkey(self):
         """bad sigkey failure case"""
         sighdr = 'SIG HEADER 99'
-        self.isdir.side_effect = [True]
-        self.get_rpm.side_effect = [{'build_id': 100, 'external_repo_id': None}]
+        self.isdir.return_value = True
+        self.get_rpm.return_value = {'build_id': 100, 'external_repo_id': None}
 
-        with self.assertRaises(koji.GenericError):
-            kojihub.add_rpm_sig(1, sighdr, sigkey='foo/bar !')
+        badkeys = [
+            'white space',
+            'badchar!',
+            '.hidden',
+            'sub/dir',
+            'hasUPPERcase',
+        ]
+        for sigkey in badkeys:
+            with self.assertRaises(koji.GenericError):
+                kojihub.add_rpm_sig(1, sighdr, sigkey=sigkey)
 
         self.assertEqual(len(self.inserts), 0)
         self.open.assert_not_called()
-        self.isdir.assert_called_once()
+        self.isdir.assert_called()
 
 
 class TestScanHeaderOnly(unittest.TestCase):