diff --git a/prometheus_client/metrics.py b/prometheus_client/metrics.py
index be61f05c..0a562e74 100644
--- a/prometheus_client/metrics.py
+++ b/prometheus_client/metrics.py
@@ -11,7 +11,7 @@
     Metric, METRIC_LABEL_NAME_RE, METRIC_NAME_RE,
     RESERVED_METRIC_LABEL_NAME_RE,
 )
-from .registry import CollectorRegistry, REGISTRY
+from .registry import Registerer, REGISTRY
 from .samples import Exemplar, Sample
 from .utils import floatToGoString, INF
 
@@ -107,7 +107,7 @@ def __init__(self: T,
                  namespace: str = '',
                  subsystem: str = '',
                  unit: str = '',
-                 registry: Optional[CollectorRegistry] = REGISTRY,
+                 registry: Optional[Registerer] = REGISTRY,
                  _labelvalues: Optional[Sequence[str]] = None,
                  ) -> None:
         self._name = _build_full_name(self._type, name, namespace, subsystem, unit)
@@ -677,7 +677,7 @@ def __init__(self,
                  namespace: str = '',
                  subsystem: str = '',
                  unit: str = '',
-                 registry: Optional[CollectorRegistry] = REGISTRY,
+                 registry: Optional[Registerer] = REGISTRY,
                  _labelvalues: Optional[Sequence[str]] = None,
                  states: Optional[Sequence[str]] = None,
                  ):
diff --git a/prometheus_client/registry.py b/prometheus_client/registry.py
index fe435cd1..899223b2 100644
--- a/prometheus_client/registry.py
+++ b/prometheus_client/registry.py
@@ -1,9 +1,15 @@
 import copy
 from threading import Lock
+from typing import Protocol
 
 from .metrics_core import Metric
 
 
+class Registerer(Protocol):
+    def register(self, collector) -> None:
+        pass
+
+
 class CollectorRegistry:
     """Metric collector registry.