diff --git a/gunicorn/config.py b/gunicorn/config.py
index 79662e4c..52215b56 100644
--- a/gunicorn/config.py
+++ b/gunicorn/config.py
@@ -103,18 +103,20 @@ class Config(object):
     def worker_class_str(self):
         uri = self.settings['worker_class'].get()
 
-        # are we using a threaded worker?
-        is_sync = uri.endswith('SyncWorker') or uri == 'sync'
-        if is_sync and self.threads > 1:
-            return "gthread"
-        return uri
+        if isinstance(uri, str):
+            # are we using a threaded worker?
+            is_sync = uri.endswith('SyncWorker') or uri == 'sync'
+            if is_sync and self.threads > 1:
+                return "gthread"
+            return uri
+        return uri.__name__
 
     @property
     def worker_class(self):
         uri = self.settings['worker_class'].get()
 
         # are we using a threaded worker?
-        is_sync = uri.endswith('SyncWorker') or uri == 'sync'
+        is_sync = isinstance(uri, str) and (uri.endswith('SyncWorker') or uri == 'sync')
         if is_sync and self.threads > 1:
             uri = "gunicorn.workers.gthread.ThreadWorker"
 
diff --git a/tests/test_config.py b/tests/test_config.py
index c094f6a2..f0ab392c 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -13,6 +13,7 @@ from gunicorn import config
 from gunicorn.app.base import Application
 from gunicorn.app.wsgiapp import WSGIApplication
 from gunicorn.errors import ConfigError
+from gunicorn.util import load_class
 from gunicorn.workers.sync import SyncWorker
 from gunicorn import glogging
 from gunicorn.instrument import statsd
@@ -55,6 +56,10 @@ class NoConfigApp(Application):
         pass
 
 
+class CustomWorker(SyncWorker):
+    pass
+
+
 class WSGIApp(WSGIApplication):
     def __init__(self):
         super().__init__("no_usage", prog="gunicorn_test")
@@ -63,6 +68,18 @@ class WSGIApp(WSGIApplication):
         pass
 
 
+def test_worker_class():
+
+    c = config.Config()
+    c.set("worker_class", CustomWorker)
+    assert c.worker_class == CustomWorker
+
+    try:
+        assert isinstance(load_class(c.worker_class), object)
+    except AttributeError:
+        pytest.fail("'load_class doesn't support type class argument'")
+
+
 def test_defaults():
     c = config.Config()
     for s in config.KNOWN_SETTINGS: