diff --git a/dom/src/storage/nsDOMStoragePersistentDB.cpp b/dom/src/storage/nsDOMStoragePersistentDB.cpp
index ed00c6a1fe0..fe491706030 100644
--- a/dom/src/storage/nsDOMStoragePersistentDB.cpp
+++ b/dom/src/storage/nsDOMStoragePersistentDB.cpp
@@ -744,7 +744,7 @@ nsDOMStoragePersistentDB::SetKey(DOMStorageImpl* aStorage,
   NS_ENSURE_SUCCESS(rv, rv);
 
   if (!aStorage->GetQuotaDomainDBKey(!aExcludeOfflineFromUsage).IsEmpty()) {
-    mCachedOwner = aStorage->GetQuotaDomainDBKey(!aExcludeOfflineFromUsage);
+    // No need to set mCachedOwner since it was set by GetUsage()
     mCachedUsage = usage;
   }
 
@@ -807,8 +807,10 @@ nsDOMStoragePersistentDB::RemoveKey(DOMStorageImpl* aStorage,
 
   mozStorageStatementScoper scope(mRemoveKeyStatement);
 
-  if (aStorage->GetQuotaDomainDBKey(!aExcludeOfflineFromUsage) == mCachedOwner) {
-    mCachedUsage -= aKeyUsage;
+  if (DomainMaybeCached(
+      aStorage->GetQuotaDomainDBKey(!aExcludeOfflineFromUsage))) {
+    mCachedUsage = 0;
+    mCachedOwner.Truncate();
   }
 
   Binder binder(mRemoveKeyStatement, &rv);
@@ -877,15 +879,15 @@ nsDOMStoragePersistentDB::RemoveOwner(const nsACString& aOwner,
   nsCAutoString subdomainsDBKey;
   nsDOMStorageDBWrapper::CreateDomainScopeDBKey(aOwner, subdomainsDBKey);
 
-  if (!aIncludeSubDomains)
-    subdomainsDBKey.AppendLiteral(":");
-  subdomainsDBKey.AppendLiteral("*");
-
-  if (subdomainsDBKey == mCachedOwner) {
+  if (DomainMaybeCached(subdomainsDBKey)) {
     mCachedUsage = 0;
     mCachedOwner.Truncate();
   }
 
+  if (!aIncludeSubDomains)
+    subdomainsDBKey.AppendLiteral(":");
+  subdomainsDBKey.AppendLiteral("*");
+
   Binder binder(mRemoveOwnerStatement, &rv);
   NS_ENSURE_SUCCESS(rv, rv);
 
@@ -960,6 +962,11 @@ nsDOMStoragePersistentDB::RemoveOwners(const nsTArray<nsString> &aOwners,
     rv = nsDOMStorageDBWrapper::CreateDomainScopeDBKey(
       NS_ConvertUTF16toUTF8(aOwners[i]), quotaKey);
 
+    if (DomainMaybeCached(quotaKey)) {
+      mCachedUsage = 0;
+      mCachedOwner.Truncate();
+    }
+
     if (!aIncludeSubDomains)
       quotaKey.AppendLiteral(":");
     quotaKey.AppendLiteral("*");
@@ -1120,3 +1127,17 @@ nsDOMStoragePersistentDB::MaybeCommitInsertTransaction()
 
   return NS_OK;
 }
+
+bool
+nsDOMStoragePersistentDB::DomainMaybeCached(const nsACString& aDomain)
+{
+  if (mCachedOwner.IsEmpty())
+    return false;
+
+  // if cached owner contains colon we must ignore it
+  if (mCachedOwner[mCachedOwner.Length() - 1] == ':')
+    return StringBeginsWith(aDomain, Substring(mCachedOwner, 0,
+                                               mCachedOwner.Length() - 1));
+  else
+    return StringBeginsWith(aDomain, mCachedOwner);
+}
diff --git a/dom/src/storage/nsDOMStoragePersistentDB.h b/dom/src/storage/nsDOMStoragePersistentDB.h
index ad9cd531e03..068e71c6ee0 100644
--- a/dom/src/storage/nsDOMStoragePersistentDB.h
+++ b/dom/src/storage/nsDOMStoragePersistentDB.h
@@ -219,6 +219,11 @@ protected:
   friend class nsDOMStorageMemoryDB;
   nsresult
   GetUsageInternal(const nsACString& aQuotaDomainDBKey, bool aExcludeOfflineFromUsage, PRInt32 *aUsage);
+
+  // Compares aDomain with the mCachedOwner and returns false if changes
+  // in aDomain don't affect mCachedUsage.
+  bool DomainMaybeCached(const nsACString& aDomain);
+
 };
 
 #endif /* nsDOMStorageDB_h___ */