diff --git a/mozilla/modules/libjar/nsJARChannel.cpp b/mozilla/modules/libjar/nsJARChannel.cpp
index 0a2771139ef..45a0067af76 100644
--- a/mozilla/modules/libjar/nsJARChannel.cpp
+++ b/mozilla/modules/libjar/nsJARChannel.cpp
@@ -474,7 +474,7 @@ nsJARChannel::EnsureJARFileAvailable(OnJARFileAvailableFun onJARFileAvailable,
 
         // use a file transport to serve as a data pump for the download (done
         // on some other thread)
-        rv = fts->CreateTransport(jarCacheFile, PR_WRONLY | PR_CREATE_FILE, 0, 
+        rv = fts->CreateTransport(jarCacheFile, PR_WRONLY | PR_CREATE_FILE | PR_TRUNCATE, 0664, 
                                   getter_AddRefs(mJarCacheTransport));
         if (NS_FAILED(rv)) goto error;
         rv = mJarCacheTransport->SetBufferSegmentSize(mBufferSegmentSize);
diff --git a/mozilla/netwerk/base/src/nsFileStreams.cpp b/mozilla/netwerk/base/src/nsFileStreams.cpp
index d8aa58becf5..1a0c5dd060d 100644
--- a/mozilla/netwerk/base/src/nsFileStreams.cpp
+++ b/mozilla/netwerk/base/src/nsFileStreams.cpp
@@ -418,8 +418,8 @@ nsFileOutputStream::Init(nsIFile* file, PRInt32 ioFlags, PRInt32 perm)
     nsCOMPtr<nsILocalFile> localFile = do_QueryInterface(file, &rv);
     if (NS_FAILED(rv)) return rv;
     if (ioFlags == -1)
-        ioFlags = PR_WRONLY | PR_CREATE_FILE;
-    if (perm == -1)
+        ioFlags = PR_WRONLY | PR_CREATE_FILE | PR_TRUNCATE;
+    if (perm <= 0)
         perm = 0664;
     return localFile->OpenNSPRFileDesc(ioFlags, perm, &mFD);
 }
diff --git a/mozilla/netwerk/protocol/jar/src/nsJARChannel.cpp b/mozilla/netwerk/protocol/jar/src/nsJARChannel.cpp
index 0a2771139ef..45a0067af76 100644
--- a/mozilla/netwerk/protocol/jar/src/nsJARChannel.cpp
+++ b/mozilla/netwerk/protocol/jar/src/nsJARChannel.cpp
@@ -474,7 +474,7 @@ nsJARChannel::EnsureJARFileAvailable(OnJARFileAvailableFun onJARFileAvailable,
 
         // use a file transport to serve as a data pump for the download (done
         // on some other thread)
-        rv = fts->CreateTransport(jarCacheFile, PR_WRONLY | PR_CREATE_FILE, 0, 
+        rv = fts->CreateTransport(jarCacheFile, PR_WRONLY | PR_CREATE_FILE | PR_TRUNCATE, 0664, 
                                   getter_AddRefs(mJarCacheTransport));
         if (NS_FAILED(rv)) goto error;
         rv = mJarCacheTransport->SetBufferSegmentSize(mBufferSegmentSize);