diff --git a/prometheus_client/registry.py b/prometheus_client/registry.py
index 63f8ab03..245a61c9 100644
--- a/prometheus_client/registry.py
+++ b/prometheus_client/registry.py
@@ -52,7 +52,7 @@ def register(self, collector: Collector) -> None:
             for name in names:
                 self._names_to_collectors[name] = collector
             self._collector_to_names[collector] = names
-            if self._support_collectors_without_names and not names:
+            if self._support_collectors_without_names and not names and collector not in self._collectors_without_names:
                 self._collectors_without_names.append(collector)
 
     def unregister(self, collector: Collector) -> None:
diff --git a/tests/test_core.py b/tests/test_core.py
index 2c29f79a..c71d8549 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -1078,6 +1078,27 @@ def collect(self):
         # was unregistered.
         self.assertEqual([], list(registry.restricted_registry(['foo']).collect()))
 
+    def test_register_no_names_collector_twice(self):
+        registry = CollectorRegistry(support_collectors_without_names=True)
+
+        class NamelessCollector:
+            def collect(self):
+                return [GaugeMetricFamily('foo', 'help', value=42)]
+
+        collector = NamelessCollector()
+        restricted = registry.restricted_registry(['foo'])
+        registry.register(collector)
+        registry.register(collector)
+        self.assertEqual(1, len(list(registry.collect())))
+        self.assertEqual(1, len(list(restricted.collect())))
+        registry.unregister(collector)
+        self.assertEqual([], list(registry.collect()))
+        self.assertEqual([], list(restricted.collect()))
+        registry.register(collector)
+        self.assertEqual(1, len(list(restricted.collect())))
+        registry.unregister(collector)
+        self.assertEqual([], list(restricted.collect()))
+
     def custom_collector(self, metric_family, registry):
         class CustomCollector:
             def collect(self):