diff --git a/build/automation.py.in b/build/automation.py.in
index ce30cd9a644e..ad35c6892c6a 100644
--- a/build/automation.py.in
+++ b/build/automation.py.in
@@ -418,6 +418,7 @@ user_pref("javascript.options.showInConsole", true);
 user_pref("devtools.errorconsole.enabled", true);
 user_pref("layout.debug.enable_data_xbl", true);
 user_pref("browser.EULA.override", true);
+user_pref("javascript.options.jit_hardening", true);
 user_pref("gfx.color_management.force_srgb", true);
 user_pref("network.manage-offline-status", false);
 user_pref("test.mousescroll", true);
diff --git a/dom/base/nsJSEnvironment.cpp b/dom/base/nsJSEnvironment.cpp
index f60ff12eb10f..409393fe6c24 100644
--- a/dom/base/nsJSEnvironment.cpp
+++ b/dom/base/nsJSEnvironment.cpp
@@ -937,6 +937,7 @@ static const char js_methodjit_always_str[]   = JS_OPTIONS_DOT_STR "methodjit_al
 static const char js_typeinfer_str[]          = JS_OPTIONS_DOT_STR "typeinference";
 static const char js_pccounts_content_str[]   = JS_OPTIONS_DOT_STR "pccounts.content";
 static const char js_pccounts_chrome_str[]    = JS_OPTIONS_DOT_STR "pccounts.chrome";
+static const char js_jit_hardening_str[]      = JS_OPTIONS_DOT_STR "jit_hardening";
 static const char js_memlog_option_str[] = JS_OPTIONS_DOT_STR "mem.log";
 
 int
@@ -973,6 +974,7 @@ nsJSContext::JSOptionChangedCallback(const char *pref, void *data)
                                             js_pccounts_content_str);
   bool useMethodJITAlways = Preferences::GetBool(js_methodjit_always_str);
   bool useTypeInference = !chromeWindow && Preferences::GetBool(js_typeinfer_str);
+  bool useHardening = Preferences::GetBool(js_jit_hardening_str);
   nsCOMPtr<nsIXULRuntime> xr = do_GetService(XULRUNTIME_SERVICE_CONTRACTID);
   if (xr) {
     bool safeMode = false;
@@ -984,6 +986,7 @@ nsJSContext::JSOptionChangedCallback(const char *pref, void *data)
       usePCCounts = false;
       useTypeInference = false;
       useMethodJITAlways = true;
+      useHardening = false;
     }
   }    
 
@@ -1012,6 +1015,11 @@ nsJSContext::JSOptionChangedCallback(const char *pref, void *data)
   else
     newDefaultJSOptions &= ~JSOPTION_METHODJIT_ALWAYS;
 
+  if (useHardening)
+    newDefaultJSOptions &= ~JSOPTION_SOFTEN;
+  else
+    newDefaultJSOptions |= JSOPTION_SOFTEN;
+
   if (useTypeInference)
     newDefaultJSOptions |= JSOPTION_TYPE_INFERENCE;
   else
diff --git a/js/src/jsapi.h b/js/src/jsapi.h
index fd03c0f683e8..35a98febd641 100644
--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -2177,11 +2177,12 @@ JS_StringToVersion(const char *string);
 #define JSOPTION_PCCOUNT        JS_BIT(17)      /* Collect per-op execution counts */
 
 #define JSOPTION_TYPE_INFERENCE JS_BIT(18)      /* Perform type inference. */
+#define JSOPTION_SOFTEN         JS_BIT(19)      /* Disable JIT hardening. */
 
 /* Options which reflect compile-time properties of scripts. */
 #define JSCOMPILEOPTION_MASK    (JSOPTION_XML)
 
-#define JSRUNOPTION_MASK        (JS_BITMASK(19) & ~JSCOMPILEOPTION_MASK)
+#define JSRUNOPTION_MASK        (JS_BITMASK(20) & ~JSCOMPILEOPTION_MASK)
 #define JSALLOPTION_MASK        (JSCOMPILEOPTION_MASK | JSRUNOPTION_MASK)
 
 extern JS_PUBLIC_API(uint32)
diff --git a/js/src/jscntxt.h b/js/src/jscntxt.h
index 6570c0d19556..b0c4878b6bbf 100644
--- a/js/src/jscntxt.h
+++ b/js/src/jscntxt.h
@@ -1127,6 +1127,7 @@ struct JSContext
     bool hasStrictOption() const { return hasRunOption(JSOPTION_STRICT); }
     bool hasWErrorOption() const { return hasRunOption(JSOPTION_WERROR); }
     bool hasAtLineOption() const { return hasRunOption(JSOPTION_ATLINE); }
+    bool hasJITHardeningOption() const { return !hasRunOption(JSOPTION_SOFTEN); }
 
     js::LifoAlloc &tempLifoAlloc() { return JS_THREAD_DATA(this)->tempLifoAlloc; }
     inline js::LifoAlloc &typeLifoAlloc();
diff --git a/modules/libpref/src/init/all.js b/modules/libpref/src/init/all.js
index 40b65b03717d..22d65a43ad80 100644
--- a/modules/libpref/src/init/all.js
+++ b/modules/libpref/src/init/all.js
@@ -635,6 +635,7 @@ pref("javascript.options.jitprofiling.chrome",  true);
 pref("javascript.options.pccounts.content", false);
 pref("javascript.options.pccounts.chrome",  false);
 pref("javascript.options.methodjit_always", false);
+pref("javascript.options.jit_hardening", true);
 pref("javascript.options.typeinference", true);
 // This preference limits the memory usage of javascript.
 // If you want to change these values for your device,