diff --git a/mozilla/xpcom/io/nsLocalFileOS2.cpp b/mozilla/xpcom/io/nsLocalFileOS2.cpp
index 61c92589fd7..9b4a4ddf427 100644
--- a/mozilla/xpcom/io/nsLocalFileOS2.cpp
+++ b/mozilla/xpcom/io/nsLocalFileOS2.cpp
@@ -740,8 +740,10 @@ nsLocalFile::Create(PRUint32 type, PRUint32 attributes)
 
     if (type == NORMAL_FILE_TYPE)
     {
-        PRFileDesc* file = PR_Open(mResolvedPath, PR_RDONLY | PR_CREATE_FILE | PR_APPEND, attributes);
-        if (file) PR_Close(file);
+        PRFileDesc* file = PR_Open(mResolvedPath, PR_RDONLY | PR_CREATE_FILE | PR_APPEND | PR_EXCL, attributes);
+        if (!file) return NS_ERROR_FILE_ALREADY_EXISTS;
+          
+        PR_Close(file);
         return NS_OK;
     }
 
diff --git a/mozilla/xpcom/io/nsLocalFileUnix.cpp b/mozilla/xpcom/io/nsLocalFileUnix.cpp
index d3466931496..93a5c206ba6 100644
--- a/mozilla/xpcom/io/nsLocalFileUnix.cpp
+++ b/mozilla/xpcom/io/nsLocalFileUnix.cpp
@@ -363,6 +363,9 @@ nsLocalFile::OpenANSIFileDesc(const char *mode, FILE * *_retval)
 
     return NS_ERROR_FAILURE;
 }
+static int exclusive_create(const char * path, mode_t mode) {
+  return open(path, O_WRONLY | O_CREAT | O_TRUNC | O_EXCL, mode);
+}
 
 NS_IMETHODIMP
 nsLocalFile::Create(PRUint32 type, PRUint32 permissions)
@@ -378,7 +381,7 @@ nsLocalFile::Create(PRUint32 type, PRUint32 permissions)
 #else
     int (*creationFunc)(const char *, mode_t) =
 #endif
-        type == NORMAL_FILE_TYPE ? creat : mkdir;
+        type == NORMAL_FILE_TYPE ? exclusive_create : mkdir;
 
     result = creationFunc((const char *)mPath, permissions);