--- a/browser/components/resistfingerprinting/test/browser/browser_navigator.js
+++ b/browser/components/resistfingerprinting/test/browser/browser_navigator.js
@@ -19,17 +19,17 @@ const SPOOFED_APPVERSION = {
   linux: "5.0 (X11)",
   win: "5.0 (Windows)",
   macosx: "5.0 (Macintosh)",
   android: "5.0 (Android 6.0)",
   other: "5.0 (X11)",
 };
 const SPOOFED_PLATFORM = {
   linux: "Linux x86_64",
-  win: "Win64",
+  win: "Win32",
   macosx: "MacIntel",
   android: "Linux armv7l",
   other: "Linux x86_64",
 };
 const SPOOFED_OSCPU = {
   linux: "Linux x86_64",
   win: "Windows NT 6.1; Win64; x64",
   macosx: "Intel Mac OS X 10.13",

--- a/dom/base/Navigator.cpp
+++ b/dom/base/Navigator.cpp
@@ -1544,19 +1544,17 @@ Navigator::GetPlatform(nsAString& aPlatf
   nsresult rv;
 
   nsCOMPtr<nsIHttpProtocolHandler>
     service(do_GetService(NS_NETWORK_PROTOCOL_CONTRACTID_PREFIX "http", &rv));
   NS_ENSURE_SUCCESS(rv, rv);
 
   // Sorry for the #if platform ugliness, but Communicator is likewise
   // hardcoded and we are seeking backward compatibility here (bug 47080).
-#if defined(_WIN64)
-  aPlatform.AssignLiteral("Win64");
-#elif defined(WIN32)
+#if defined(WIN32)
   aPlatform.AssignLiteral("Win32");
 #elif defined(XP_MACOSX) && defined(__ppc__)
   aPlatform.AssignLiteral("MacPPC");
 #elif defined(XP_MACOSX) && defined(__i386__)
   aPlatform.AssignLiteral("MacIntel");
 #elif defined(XP_MACOSX) && defined(__x86_64__)
   aPlatform.AssignLiteral("MacIntel");
 #else

--- a/toolkit/components/resistfingerprinting/nsRFPService.h
+++ b/toolkit/components/resistfingerprinting/nsRFPService.h
@@ -20,17 +20,17 @@
 // We decided to give different spoofed values according to the platform. The
 // reason is that it is easy to detect the real platform. So there is no benefit
 // for hiding the platform: it only brings breakages, like keyboard shortcuts won't
 // work in MAC OS if we spoof it as a window platform.
 #ifdef XP_WIN
 #define SPOOFED_UA_OS      "Windows NT 6.1; Win64; x64"
 #define SPOOFED_APPVERSION "5.0 (Windows)"
 #define SPOOFED_OSCPU      "Windows NT 6.1; Win64; x64"
-#define SPOOFED_PLATFORM   "Win64"
+#define SPOOFED_PLATFORM   "Win32"
 #elif defined(XP_MACOSX)
 #define SPOOFED_UA_OS      "Macintosh; Intel Mac OS X 10.13"
 #define SPOOFED_APPVERSION "5.0 (Macintosh)"
 #define SPOOFED_OSCPU      "Intel Mac OS X 10.13"
 #define SPOOFED_PLATFORM   "MacIntel"
 #elif defined(MOZ_WIDGET_ANDROID)
 #define SPOOFED_UA_OS      "Android 6.0; Mobile"
 #define SPOOFED_APPVERSION "5.0 (Android 6.0)"