--- a/netwerk/cookie/nsCookieService.cpp
+++ b/netwerk/cookie/nsCookieService.cpp
@@ -99,17 +99,18 @@ static nsCookieService *gCookieService;
 // XXX_hack. See bug 178993.
 // This is a hack to hide HttpOnly cookies from older browsers
 static const char kHttpOnlyPrefix[] = "#HttpOnly_";
 
 static const char kCookieFileName[] = "cookies.sqlite";
 #define COOKIES_SCHEMA_VERSION 4
 
 static const PRInt64 kCookieStaleThreshold = 60 * PR_USEC_PER_SEC; // 1 minute in microseconds
-static const PRInt64 kCookiePurgeAge = 30 * 24 * 60 * 60 * PR_USEC_PER_SEC; // 30 days in microseconds
+static const PRInt64 kCookiePurgeAge =
+  PRInt64(30 * 24 * 60 * 60) * PR_USEC_PER_SEC; // 30 days in microseconds
 
 static const char kOldCookieFileName[] = "cookies.txt";
 
 #undef  LIMIT
 #define LIMIT(x, low, high, default) ((x) >= (low) && (x) <= (high) ? (x) : (default))
 
 #undef  ADD_TEN_PERCENT
 #define ADD_TEN_PERCENT(i) ((i) + (i)/10)
@@ -1346,18 +1347,20 @@ nsCookieService::PrefChanged(nsIPrefBran
     mCookieBehavior = (PRUint8) LIMIT(val, 0, 2, 0);
 
   if (NS_SUCCEEDED(aPrefBranch->GetIntPref(kPrefMaxNumberOfCookies, &val)))
     mMaxNumberOfCookies = (PRUint16) LIMIT(val, 1, 0xFFFF, kMaxNumberOfCookies);
 
   if (NS_SUCCEEDED(aPrefBranch->GetIntPref(kPrefMaxCookiesPerHost, &val)))
     mMaxCookiesPerHost = (PRUint16) LIMIT(val, 1, 0xFFFF, kMaxCookiesPerHost);
 
-  if (NS_SUCCEEDED(aPrefBranch->GetIntPref(kPrefCookiePurgeAge, &val)))
-    mCookiePurgeAge = LIMIT(val, 0, PR_INT32_MAX, PR_INT32_MAX) * PR_USEC_PER_SEC;
+  if (NS_SUCCEEDED(aPrefBranch->GetIntPref(kPrefCookiePurgeAge, &val))) {
+    mCookiePurgeAge =
+      PRInt64(LIMIT(val, 0, PR_INT32_MAX, PR_INT32_MAX)) * PR_USEC_PER_SEC;
+  }
 
   PRBool boolval;
   if (NS_SUCCEEDED(aPrefBranch->GetBoolPref(kPrefThirdPartySession, &boolval)))
     mThirdPartySession = boolval;
 
   // Lazily instantiate the third party service if necessary.
   if (!mThirdPartyUtil && RequireThirdPartyCheck()) {
     mThirdPartyUtil = do_GetService(THIRDPARTYUTIL_CONTRACTID);