diff --git a/mozilla/modules/libpr0n/src/imgCache.cpp b/mozilla/modules/libpr0n/src/imgCache.cpp
index 18da4f33e7c..96c07f8ad79 100644
--- a/mozilla/modules/libpr0n/src/imgCache.cpp
+++ b/mozilla/modules/libpr0n/src/imgCache.cpp
@@ -211,7 +211,7 @@ PRBool imgCache::Get(nsIURI *aKey, PRBool aDoomIfExpired, imgRequest **aRequest,
   if (aDoomIfExpired) {
     PRUint32 expirationTime;
     entry->GetExpirationTime(&expirationTime);
-    if (expirationTime && (expirationTime <= SecondsFromPRTime(PR_Now()))) {
+    if (expirationTime <= SecondsFromPRTime(PR_Now())) {
       entry->Doom();
       return PR_FALSE;
     }
diff --git a/mozilla/netwerk/cache/src/nsCacheEntry.cpp b/mozilla/netwerk/cache/src/nsCacheEntry.cpp
index 5cb02d1750c..3131215e25c 100644
--- a/mozilla/netwerk/cache/src/nsCacheEntry.cpp
+++ b/mozilla/netwerk/cache/src/nsCacheEntry.cpp
@@ -40,7 +40,7 @@ nsCacheEntry::nsCacheEntry(nsCString *          key,
     : mKey(key),
       mFetchCount(0),
       mLastFetched(0),
-      mExpirationTime(0),
+      mExpirationTime(NO_EXPIRATION_TIME),
       mFlags(0),
       mDataSize(0),
       mMetaSize(0),
diff --git a/mozilla/netwerk/cache/src/nsCacheEntry.h b/mozilla/netwerk/cache/src/nsCacheEntry.h
index d954d9ed101..a373b9adb51 100644
--- a/mozilla/netwerk/cache/src/nsCacheEntry.h
+++ b/mozilla/netwerk/cache/src/nsCacheEntry.h
@@ -40,6 +40,8 @@ class nsCacheMetaData;
 class nsCacheRequest;
 class nsCacheEntryDescriptor;
 
+#define NO_EXPIRATION_TIME  0xFFFFFFFF
+
 /******************************************************************************
 * nsCacheEntry
 *******************************************************************************/
diff --git a/mozilla/netwerk/cache/src/nsCacheService.cpp b/mozilla/netwerk/cache/src/nsCacheService.cpp
index 2d72be463bc..a125cd85791 100644
--- a/mozilla/netwerk/cache/src/nsCacheService.cpp
+++ b/mozilla/netwerk/cache/src/nsCacheService.cpp
@@ -860,8 +860,7 @@ nsCacheService::ActivateEntry(nsCacheRequest * request,
 
     if (entry &&
         ((request->AccessRequested() == nsICache::ACCESS_WRITE) ||
-         (entry->mExpirationTime &&
-          entry->mExpirationTime <= SecondsFromPRTime(PR_Now()) &&
+         (entry->mExpirationTime <= SecondsFromPRTime(PR_Now()) &&
           request->WillDoomEntriesIfExpired())))
     {
         // this is FORCE-WRITE request or the entry has expired
diff --git a/mozilla/netwerk/cache/src/nsMemoryCacheDevice.cpp b/mozilla/netwerk/cache/src/nsMemoryCacheDevice.cpp
index 3f4f5d83f71..dd92fec7d0d 100644
--- a/mozilla/netwerk/cache/src/nsMemoryCacheDevice.cpp
+++ b/mozilla/netwerk/cache/src/nsMemoryCacheDevice.cpp
@@ -326,7 +326,7 @@ int
 nsMemoryCacheDevice::EvictionList(nsCacheEntry * entry, PRUint32  deltaSize)
 {
     PRUint32  size = entry->Size() + deltaSize;
-    if ((size > mEvictionThreshold) || (entry->ExpirationTime() != 0))
+    if ((size > mEvictionThreshold) || (entry->ExpirationTime() != NO_EXPIRATION_TIME))
         return mostLikelyToEvict;
     
     return leastLikelyToEvict;
diff --git a/mozilla/netwerk/protocol/http/src/nsHttpChannel.cpp b/mozilla/netwerk/protocol/http/src/nsHttpChannel.cpp
index 0c5f7f01f57..cf7a5812fde 100644
--- a/mozilla/netwerk/protocol/http/src/nsHttpChannel.cpp
+++ b/mozilla/netwerk/protocol/http/src/nsHttpChannel.cpp
@@ -743,7 +743,7 @@ nsHttpChannel::UpdateExpirationTime()
 {
     NS_ENSURE_TRUE(mResponseHead, NS_ERROR_FAILURE);
 
-    PRUint32 expirationTime = 1; // this can't be 0 unless bug 120833 is fixed
+    PRUint32 expirationTime = 0;
     if (!mResponseHead->MustValidate()) {
         PRUint32 freshnessLifetime = 0;
         nsresult rv;
diff --git a/mozilla/widget/src/cocoa/nsSound.cpp b/mozilla/widget/src/cocoa/nsSound.cpp
index f116b0f3621..95f45578849 100644
--- a/mozilla/widget/src/cocoa/nsSound.cpp
+++ b/mozilla/widget/src/cocoa/nsSound.cpp
@@ -408,7 +408,7 @@ nsSound::PutSoundInCache(nsIChannel* inChannel, PRUint32 inDataSize, nsISupports
     }
   }
   
-  if (expirationTime == 0)
+  if (expirationTime == PRUint32(-1))   // no expiration time (never expires)
   {
     // set it to some reasonable default, like now + 24 hours
     expirationTime = SecondsFromPRTime(PR_Now()) + 60 * 60 * 24;
diff --git a/mozilla/widget/src/mac/nsSound.cpp b/mozilla/widget/src/mac/nsSound.cpp
index 515adfd56df..f5878b9f465 100644
--- a/mozilla/widget/src/mac/nsSound.cpp
+++ b/mozilla/widget/src/mac/nsSound.cpp
@@ -408,7 +408,7 @@ nsSound::PutSoundInCache(nsIChannel* inChannel, PRUint32 inDataSize, nsISupports
     }
   }
   
-  if (expirationTime == 0)
+  if (expirationTime == PRUint32(-1))   // no expiration time (never expires)
   {
     // set it to some reasonable default, like now + 24 hours
     expirationTime = SecondsFromPRTime(PR_Now()) + 60 * 60 * 24;