diff --git a/Lib/fontTools/ttLib/tables/otBase.py b/Lib/fontTools/ttLib/tables/otBase.py
index a99d55997..c9e167918 100644
--- a/Lib/fontTools/ttLib/tables/otBase.py
+++ b/Lib/fontTools/ttLib/tables/otBase.py
@@ -110,11 +110,14 @@ class BaseTTXConverter(DefaultTable):
 						return writer.getAllDataUsingHarfbuzz()
 					except (ValueError, MemoryError, hb.RepackerError) as e:
 						if use_hb_repack is None:
+							error_msg = f"{type(e).__name__}"
+							if str(e) != "":
+								error_msg += f": {e}"
 							log.error(
 								"hb.repack failed to serialize '%s', reverting to "
 								"pure-python serializer; the error message was: %s",
 								self.tableTag,
-								e,
+								error_msg,
 							)
 							return writer.getAllData(remove_duplicate=False)
 						# let the error propagate if USE_HARFBUZZ_REPACKER is True
diff --git a/Tests/subset/subset_test.py b/Tests/subset/subset_test.py
index e555453e2..07c47b515 100644
--- a/Tests/subset/subset_test.py
+++ b/Tests/subset/subset_test.py
@@ -803,7 +803,7 @@ class SubsetTest:
         "installed, enabled, ok",
         [
             pytest.param(True, None, True, id="installed-auto-ok"),
-            pytest.param(True, None, True, id="installed-auto-fail"),
+            pytest.param(True, None, False, id="installed-auto-fail"),
             pytest.param(True, True, True, id="installed-enabled-ok"),
             pytest.param(True, True, False, id="installed-enabled-fail"),
             pytest.param(True, False, True, id="installed-disabled"),
@@ -887,7 +887,7 @@ class SubsetTest:
         assert (
                 (
                 "hb.repack failed to serialize 'GSUB', reverting to "
-                "pure-python serializer; the error message was: mocking"
+                "pure-python serializer; the error message was: RepackerError: mocking"
             ) in caplog.text
         ) ^ ok