diff --git a/scrapy/utils/datatypes.py b/scrapy/utils/datatypes.py
index 4e65c062e..dd0e062d0 100644
--- a/scrapy/utils/datatypes.py
+++ b/scrapy/utils/datatypes.py
@@ -152,7 +152,9 @@ class LocalCache(OrderedDict[_KT, _VT]):
         self.limit: int | None = limit
 
     def __setitem__(self, key: _KT, value: _VT) -> None:
-        if self.limit:
+        if self.limit is not None:
+            if self.limit == 0:
+                return
             while len(self) >= self.limit:
                 self.popitem(last=False)
         super().__setitem__(key, value)
diff --git a/tests/test_resolver.py b/tests/test_resolver.py
index 83fc8693b..7cca45ed1 100644
--- a/tests/test_resolver.py
+++ b/tests/test_resolver.py
@@ -53,3 +53,21 @@ def test_caching_hostname_resolver_no_addresses_not_cached():
     resolver.resolveHostName(Mock(), "example.com")
 
     assert "example.com" not in dnscache
+
+
+def test_caching_hostname_resolver_dnscache_disabled_rejects_storage():
+
+    def fake_resolve(receiver, *_):
+        receiver.resolutionBegan(Mock())
+        receiver.addressResolved(Mock())
+        receiver.resolutionComplete()
+        return receiver
+
+    reactor = Mock()
+    reactor.nameResolver.resolveHostName.side_effect = fake_resolve
+
+    resolver = CachingHostnameResolver(reactor, cache_size=0)
+    resolver.resolveHostName(Mock(), "example.com")
+
+    assert "example.com" not in dnscache
+    assert len(dnscache) == 0
diff --git a/tests/test_utils_datatypes.py b/tests/test_utils_datatypes.py
index ba6b82503..fe1f60c7d 100644
--- a/tests/test_utils_datatypes.py
+++ b/tests/test_utils_datatypes.py
@@ -309,6 +309,16 @@ class TestLocalCache:
             assert str(x) in cache
             assert cache[str(x)] == x
 
+    def test_cache_with_zero_limit(self):
+        cache = LocalCache(limit=0)
+        cache["a"] = 1
+        cache["b"] = 2
+        cache["c"] = 3
+        assert len(cache) == 0
+        assert "a" not in cache
+        assert "b" not in cache
+        assert "c" not in cache
+
 
 class TestLocalWeakReferencedCache:
     def test_cache_with_limit(self):