diff --git a/js/rust/build.rs b/js/rust/build.rs
index 29e21dbfddef..3223d366534a 100644
--- a/js/rust/build.rs
+++ b/js/rust/build.rs
@@ -170,7 +170,7 @@ const WHITELIST_TYPES: &'static [&'static str] = &[
     "JS::HandleValue",
     "JS::HandleValueArray",
     "JS::IsAcceptableThis",
-    "JSAutoRealmAllowCCW",
+    "JSAutoRealm",
     "JSAutoStructuredCloneBuffer",
     "JSClass",
     "JSClassOps",
diff --git a/js/rust/src/ar.rs b/js/rust/src/ar.rs
index b79bb739f345..d65fbe59092b 100644
--- a/js/rust/src/ar.rs
+++ b/js/rust/src/ar.rs
@@ -3,7 +3,7 @@ use jsapi::root::*;
 use std::ptr;
 
 #[derive(Debug)]
-pub struct AutoRealm(JSAutoRealmAllowCCW);
+pub struct AutoRealm(JSAutoRealm);
 
 impl AutoRealm {
     #[cfg(feature = "debugmozjs")]
@@ -16,7 +16,7 @@ impl AutoRealm {
         };
 
         AutoRealm(
-            JSAutoRealmAllowCCW::new(
+            JSAutoRealm::new(
                 cx,
                 target,
                 &mut notifier as *mut _))
@@ -27,7 +27,7 @@ impl AutoRealm {
                            target: *mut JSObject)
                            -> AutoRealm
     {
-        AutoRealm(JSAutoRealmAllowCCW::new(cx, target))
+        AutoRealm(JSAutoRealm::new(cx, target))
     }
 
     #[cfg(feature = "debugmozjs")]
@@ -40,7 +40,7 @@ impl AutoRealm {
         };
 
         AutoRealm(
-            JSAutoRealmAllowCCW::new1(
+            JSAutoRealm::new1(
                 cx,
                 target,
                 &mut notifier as *mut _))
@@ -51,6 +51,6 @@ impl AutoRealm {
                               target: *mut JSScript)
                               -> AutoRealm
     {
-        AutoRealm(JSAutoRealmAllowCCW::new1(cx, target))
+        AutoRealm(JSAutoRealm::new1(cx, target))
     }
 }
diff --git a/js/rust/src/rust.rs b/js/rust/src/rust.rs
index b8ba11e383a1..c285fcf8a55e 100644
--- a/js/rust/src/rust.rs
+++ b/js/rust/src/rust.rs
@@ -620,7 +620,7 @@ impl GCMethods for JS::Value {
 // ___________________________________________________________________________
 // Implementations for various things in jsapi.rs
 
-impl Drop for JSAutoRealmAllowCCW {
+impl Drop for JSAutoRealm {
     fn drop(&mut self) {
         unsafe { JS::LeaveRealm(self.cx_, self.oldRealm_); }
     }
diff --git a/js/src/devtools/rootAnalysis/annotations.js b/js/src/devtools/rootAnalysis/annotations.js
index 7f9e82b5bd56..c3c55dc907e5 100644
--- a/js/src/devtools/rootAnalysis/annotations.js
+++ b/js/src/devtools/rootAnalysis/annotations.js
@@ -198,11 +198,6 @@ var ignoreFunctions = {
     // FIXME!
     "NS_DebugBreak": true,
 
-    // These are a little overzealous -- these destructors *can* GC if they end
-    // up wrapping a pending exception. See bug 898815 for the heavyweight fix.
-    "void js::AutoRealm::~AutoRealm(int32)" : true,
-    "void JSAutoRealmAllowCCW::~JSAutoRealmAllowCCW(int32)" : true,
-
     // Similar to heap snapshot mock classes, and GTests below. This posts a
     // synchronous runnable when a GTest fails, and we are pretty sure that the
     // particular runnable it posts can't even GC, but the analysis isn't
diff --git a/js/src/jsapi.cpp b/js/src/jsapi.cpp
index 1cea7c605f9e..04e84f7584df 100644
--- a/js/src/jsapi.cpp
+++ b/js/src/jsapi.cpp
@@ -691,6 +691,8 @@ JS::EnterRealm(JSContext* cx, JSObject* target)
     AssertHeapIsIdle();
     CHECK_REQUEST(cx);
 
+    MOZ_DIAGNOSTIC_ASSERT(!js::IsCrossCompartmentWrapper(target));
+
     Realm* oldRealm = cx->realm();
     cx->enterRealmOf(target);
     return oldRealm;
@@ -704,44 +706,30 @@ JS::LeaveRealm(JSContext* cx, JS::Realm* oldRealm)
     cx->leaveRealm(oldRealm);
 }
 
-JSAutoRealmAllowCCW::JSAutoRealmAllowCCW(JSContext* cx, JSObject* target
-                                         MOZ_GUARD_OBJECT_NOTIFIER_PARAM_IN_IMPL)
-  : cx_(cx),
-    oldRealm_(cx->realm())
-{
-    AssertHeapIsIdleOrIterating();
-    MOZ_GUARD_OBJECT_NOTIFIER_INIT;
-    cx_->enterRealmOf(target);
-}
-
-JSAutoRealmAllowCCW::JSAutoRealmAllowCCW(JSContext* cx, JSScript* target
-                                         MOZ_GUARD_OBJECT_NOTIFIER_PARAM_IN_IMPL)
-  : cx_(cx),
-    oldRealm_(cx->realm())
-{
-    AssertHeapIsIdleOrIterating();
-    MOZ_GUARD_OBJECT_NOTIFIER_INIT;
-    cx_->enterRealmOf(target);
-}
-
-JSAutoRealmAllowCCW::~JSAutoRealmAllowCCW()
-{
-    cx_->leaveRealm(oldRealm_);
-}
-
 JSAutoRealm::JSAutoRealm(JSContext* cx, JSObject* target
                          MOZ_GUARD_OBJECT_NOTIFIER_PARAM_IN_IMPL)
-  : JSAutoRealmAllowCCW(cx, target)
+  : cx_(cx),
+    oldRealm_(cx->realm())
 {
     MOZ_GUARD_OBJECT_NOTIFIER_INIT;
     MOZ_DIAGNOSTIC_ASSERT(!js::IsCrossCompartmentWrapper(target));
+    AssertHeapIsIdleOrIterating();
+    cx_->enterRealmOf(target);
 }
 
 JSAutoRealm::JSAutoRealm(JSContext* cx, JSScript* target
                          MOZ_GUARD_OBJECT_NOTIFIER_PARAM_IN_IMPL)
-  : JSAutoRealmAllowCCW(cx, target)
+  : cx_(cx),
+    oldRealm_(cx->realm())
 {
     MOZ_GUARD_OBJECT_NOTIFIER_INIT;
+    AssertHeapIsIdleOrIterating();
+    cx_->enterRealmOf(target);
+}
+
+JSAutoRealm::~JSAutoRealm()
+{
+    cx_->leaveRealm(oldRealm_);
 }
 
 JSAutoNullableRealm::JSAutoNullableRealm(JSContext* cx,
@@ -750,12 +738,14 @@ JSAutoNullableRealm::JSAutoNullableRealm(JSContext* cx,
   : cx_(cx),
     oldRealm_(cx->realm())
 {
-    AssertHeapIsIdleOrIterating();
     MOZ_GUARD_OBJECT_NOTIFIER_INIT;
-    if (targetOrNull)
+    AssertHeapIsIdleOrIterating();
+    if (targetOrNull) {
+        MOZ_DIAGNOSTIC_ASSERT(!js::IsCrossCompartmentWrapper(targetOrNull));
         cx_->enterRealmOf(targetOrNull);
-    else
+    } else {
         cx_->enterNullRealm();
+    }
 }
 
 JSAutoNullableRealm::~JSAutoNullableRealm()
diff --git a/js/src/jsapi.h b/js/src/jsapi.h
index 3697499308ee..d6052e23701a 100644
--- a/js/src/jsapi.h
+++ b/js/src/jsapi.h
@@ -858,10 +858,13 @@ JS_RefreshCrossCompartmentWrappers(JSContext* cx, JS::Handle<JSObject*> obj);
  *     {
  *       JSAutoRealm ar(cx, obj);  // constructor enters
  *       // in the realm of 'obj'
- *     }                                 // destructor leaves
+ *     }                           // destructor leaves
  *     // back in realm 'r'
  *   }
  *
+ * The object passed to JSAutoRealm must *not* be a cross-compartment wrapper,
+ * because CCWs are not associated with a single realm.
+ *
  * For more complicated uses that don't neatly fit in a C++ stack frame, the
  * realm can be entered and left using separate function calls:
  *
@@ -882,27 +885,14 @@ JS_RefreshCrossCompartmentWrappers(JSContext* cx, JS::Handle<JSObject*> obj);
  * the JSAutoRealm.
  */
 
-// JSAutoRealmAllowCCW is deprecated and will be removed soon, because entering
-// the realm of a CCW doesn't make sense when CCWs are shared by all realms in
-// the compartment. New code should prefer JSAutoRealm below instead (it asserts
-// the object is not a CCW).
-class MOZ_RAII JS_PUBLIC_API(JSAutoRealmAllowCCW)
+class MOZ_RAII JS_PUBLIC_API(JSAutoRealm)
 {
     JSContext* cx_;
     JS::Realm* oldRealm_;
-  public:
-    JSAutoRealmAllowCCW(JSContext* cx, JSObject* target MOZ_GUARD_OBJECT_NOTIFIER_PARAM);
-    JSAutoRealmAllowCCW(JSContext* cx, JSScript* target MOZ_GUARD_OBJECT_NOTIFIER_PARAM);
-    ~JSAutoRealmAllowCCW();
-
-    MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
-};
-
-class MOZ_RAII JS_PUBLIC_API(JSAutoRealm) : public JSAutoRealmAllowCCW
-{
   public:
     JSAutoRealm(JSContext* cx, JSObject* target MOZ_GUARD_OBJECT_NOTIFIER_PARAM);
     JSAutoRealm(JSContext* cx, JSScript* target MOZ_GUARD_OBJECT_NOTIFIER_PARAM);
+    ~JSAutoRealm();
 
     MOZ_DECL_USE_GUARD_OBJECT_NOTIFIER
 };
@@ -922,6 +912,9 @@ class MOZ_RAII JS_PUBLIC_API(JSAutoNullableRealm)
 namespace JS {
 
 /** NB: This API is infallible; a nullptr return value does not indicate error.
+ *
+ * |target| must not be a cross-compartment wrapper because CCWs are not
+ * associated with a single realm.
  *
  * Entering a realm roots the realm and its global object until the matching
  * JS::LeaveRealm() call.