diff --git a/django/core/cache/backends/locmem.py b/django/core/cache/backends/locmem.py
index 245c170bb4..44d7db62c3 100644
--- a/django/core/cache/backends/locmem.py
+++ b/django/core/cache/backends/locmem.py
@@ -9,16 +9,17 @@ except ImportError:
 from django.core.cache.backends.base import BaseCache, DEFAULT_TIMEOUT
 from django.utils.synch import RWLock
 
+
 # Global in-memory store of cache data. Keyed by name, to provide
 # multiple named local memory caches.
 _caches = {}
 _expire_info = {}
 _locks = {}
 
+
 class LocMemCache(BaseCache):
     def __init__(self, name, params):
         BaseCache.__init__(self, params)
-        global _caches, _expire_info, _locks
         self._cache = _caches.setdefault(name, {})
         self._expire_info = _expire_info.setdefault(name, {})
         self._lock = _locks.setdefault(name, RWLock())
@@ -45,11 +46,11 @@ class LocMemCache(BaseCache):
             exp = self._expire_info.get(key, 0)
             if exp is None or exp > time.time():
                 pickled = self._cache[key]
-        try:
-            if pickled is not None:
+        if pickled is not None:
+            try:
                 return pickle.loads(pickled)
-        except pickle.PickleError:
-            return default
+            except pickle.PickleError:
+                return default
 
         with self._lock.writer():
             try:
@@ -73,11 +74,12 @@ class LocMemCache(BaseCache):
         self.validate_key(key)
         try:
             pickled = pickle.dumps(value, pickle.HIGHEST_PROTOCOL)
-            with self._lock.writer():
-                self._set(key, pickled, timeout)
         except pickle.PickleError:
             pass
-            
+        else:
+            with self._lock.writer():
+                self._set(key, pickled, timeout)
+
     def incr(self, key, delta=1, version=None):
         value = self.get(key, version=version)
         if value is None:
@@ -86,10 +88,11 @@ class LocMemCache(BaseCache):
         key = self.make_key(key, version=version)
         try:
             pickled = pickle.dumps(new_value, pickle.HIGHEST_PROTOCOL)
-            with self._lock.writer():
-                self._cache[key] = pickled
         except pickle.PickleError:
             pass
+        else:
+            with self._lock.writer():
+                self._cache[key] = pickled
         return new_value
 
     def has_key(self, key, version=None):
@@ -138,6 +141,7 @@ class LocMemCache(BaseCache):
         self._cache.clear()
         self._expire_info.clear()
 
+
 # For backwards compatibility
 class CacheClass(LocMemCache):
     pass