diff --git a/tests/core/test_prometheus.py b/tests/core/test_prometheus.py
index e7cf72b..2f6c239 100644
--- a/tests/core/test_prometheus.py
+++ b/tests/core/test_prometheus.py
@@ -69,7 +69,7 @@ rpc_count 30
     assert [s.name for s in fams["req_seconds"].samples] == [
         "req_seconds_bucket", "req_seconds_bucket", "req_seconds_sum", "req_seconds_count",
     ]
-    assert math.isinf(fams["req_seconds"].samples[1].value)
+    assert fams["req_seconds"].samples[1].label_dict() == {"le": "+Inf"}
     assert [s.name for s in fams["rpc"].samples] == ["rpc", "rpc_sum", "rpc_count"]