diff --git a/src/c/misc_thread_common.h b/src/c/misc_thread_common.h
index ca12d4d6..d8d81824 100644
--- a/src/c/misc_thread_common.h
+++ b/src/c/misc_thread_common.h
@@ -204,6 +204,10 @@ thread_canary_register(PyThreadState *tstate)
     if (tdict == NULL)
         goto ignore_error;
 
+    /* Give ThreadCanary_Type a valid metatype before instantiating it. */
+    if (PyType_Ready(&ThreadCanary_Type) < 0)
+        goto ignore_error;
+
     canary = PyObject_New(ThreadCanaryObj, &ThreadCanary_Type);
     //fprintf(stderr, "thread_canary_register(%p): tstate=%p tls=%p\n", canary, tstate, tls);
     if (canary == NULL)