diff --git a/dns/resolver.py b/dns/resolver.py
index ed4e8661..3ba76e31 100644
--- a/dns/resolver.py
+++ b/dns/resolver.py
@@ -36,6 +36,7 @@
 import dns.ipv6
 import dns.message
 import dns.name
+import dns.rdata
 import dns.nameserver
 import dns.query
 import dns.rcode
@@ -297,7 +298,7 @@ def __getattr__(self, attr):  # pragma: no cover
     def __len__(self) -> int:
         return self.rrset and len(self.rrset) or 0
 
-    def __iter__(self):
+    def __iter__(self) -> Iterator[dns.rdata.Rdata]:
         return self.rrset and iter(self.rrset) or iter(tuple())
 
     def __getitem__(self, i):