--- a/toolkit/components/resistfingerprinting/nsRFPService.cpp
+++ b/toolkit/components/resistfingerprinting/nsRFPService.cpp
@@ -157,24 +157,24 @@ nsRFPService::UpdatePref()
       }
       // PR_SetEnv() needs the input string been leaked intentionally, so
       // we copy it here.
       tz = ToNewCString(tzValue);
       if (tz) {
         PR_SetEnv(tz);
       }
     } else {
-#if defined(XP_LINUX) || defined (XP_MACOSX)
+#if defined(XP_WIN)
+      // For Windows, we reset the TZ to an empty string. This will make Windows to use
+      // its system timezone.
+      PR_SetEnv("TZ=");
+#else
       // For POSIX like system, we reset the TZ to the /etc/localtime, which is the
       // system timezone.
       PR_SetEnv("TZ=:/etc/localtime");
-#else
-      // For Windows, we reset the TZ to an empty string. This will make Windows to use
-      // its system timezone.
-      PR_SetEnv("TZ=");
 #endif
     }
   }
 
   nsJSUtils::ResetTimeZone();
 }
 
 void