--- a/netwerk/protocol/http/nsHttpChannel.cpp
+++ b/netwerk/protocol/http/nsHttpChannel.cpp
@@ -78,16 +78,20 @@
 #include "nsIX509Cert.h"
 #include "ScopedNSSTypes.h"
 #include "nsNullPrincipal.h"
 
 namespace mozilla { namespace net {
 
 namespace {
 
+// Monotonically increasing ID for generating unique cache entries per
+// intercepted channel.
+static uint64_t gNumIntercepted = 0;
+
 // True if the local cache should be bypassed when processing a request.
 #define BYPASS_LOCAL_CACHE(loadFlags) \
         (loadFlags & (nsIRequest::LOAD_BYPASS_CACHE | \
                       nsICachingChannel::LOAD_BYPASS_LOCAL_CACHE))
 
 #define RECOVER_FROM_CACHE_FILE_ERROR(result) \
         ((result) == NS_ERROR_FILE_NOT_FOUND || \
          (result) == NS_ERROR_FILE_CORRUPTED || \
@@ -218,16 +222,17 @@ AutoRedirectVetoNotifier::ReportRedirect
 
 nsHttpChannel::nsHttpChannel()
     : HttpAsyncAborter<nsHttpChannel>(this)
     , mLogicalOffset(0)
     , mPostID(0)
     , mRequestTime(0)
     , mOfflineCacheLastModifiedTime(0)
     , mInterceptCache(DO_NOT_INTERCEPT)
+    , mInterceptionID(gNumIntercepted++)
     , mCachedContentIsValid(false)
     , mCachedContentIsPartial(false)
     , mCacheOnlyMetadata(false)
     , mTransactionReplaced(false)
     , mAuthRetryPending(false)
     , mProxyAuthPending(false)
     , mResuming(false)
     , mInitedCacheEntry(false)
@@ -2777,17 +2782,17 @@ nsHttpChannel::OpenCacheEntry(bool isHtt
     // When removed, remove the flags and related code snippets.
     if (mLoadFlags & LOAD_BYPASS_LOCAL_CACHE_IF_BUSY)
         cacheEntryOpenFlags |= nsICacheStorage::OPEN_BYPASS_IF_BUSY;
 
     if (mPostID) {
         extension.Append(nsPrintfCString("%d", mPostID));
     }
     if (PossiblyIntercepted()) {
-        extension.Append('u');
+        extension.Append(nsPrintfCString("u%lld", mInterceptionID));
     }
 
     // If this channel should be intercepted, we do not open a cache entry for this channel
     // until the interception process is complete and the consumer decides what to do with it.
     if (mInterceptCache == MAYBE_INTERCEPT) {
         nsCOMPtr<nsICacheEntry> entry;
         rv = cacheStorage->OpenTruncate(openURI, extension, getter_AddRefs(entry));
         NS_ENSURE_SUCCESS(rv, rv);

--- a/netwerk/protocol/http/nsHttpChannel.h
+++ b/netwerk/protocol/http/nsHttpChannel.h
@@ -413,16 +413,18 @@ private:
     nsCOMPtr<nsIHttpChannelAuthProvider> mAuthProvider;
 
     // States of channel interception
     enum {
         DO_NOT_INTERCEPT,  // no interception will occur
         MAYBE_INTERCEPT,   // interception in progress, but can be cancelled
         INTERCEPTED,       // a synthesized response has been provided
     } mInterceptCache;
+    // Unique ID of this channel for the interception purposes.
+    const uint64_t mInterceptionID;
 
     bool PossiblyIntercepted() {
         return mInterceptCache != DO_NOT_INTERCEPT;
     }
 
     // If the channel is associated with a cache, and the URI matched
     // a fallback namespace, this will hold the key for the fallback
     // cache entry.