diff --git a/msgspec/_core.c b/msgspec/_core.c
index 738546e6..160df06d 100644
--- a/msgspec/_core.c
+++ b/msgspec/_core.c
@@ -4621,11 +4621,15 @@ typenode_origin_args_metadata(
          * abstract -> concrete mapping. If present, this is an unparametrized
          * collection of some form. This helps avoid compatibility issues in
          * Python 3.8, where unparametrized collections still have __args__. */
-        origin = PyDict_GetItem(state->mod->concrete_types, t);
+        origin = PyDict_GetItemWithError(state->mod->concrete_types, t);
         if (origin != NULL) {
             Py_INCREF(origin);
             break;
         }
+        else {
+            /* Ignore all errors in this initial check */
+            PyErr_Clear();
+        }
 
         /* If `t` is a type instance, no need to inspect further */
         if (PyType_CheckExact(t)) {
diff --git a/setup.cfg b/setup.cfg
index 86465ce0..4e937c4d 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -12,6 +12,8 @@ omit =
 markers =
     mypy
     pyright
+filterwarnings =
+    error
 
 [versioneer]
 VCS = git