diff --git a/js/src/jit-test/tests/basic/testBug895774.js b/js/src/jit-test/tests/basic/testBug895774.js
new file mode 100644
index 000000000000..872e3e42c9d9
--- /dev/null
+++ b/js/src/jit-test/tests/basic/testBug895774.js
@@ -0,0 +1,14 @@
+var g1 = newGlobal();
+var g2 = newGlobal();
+g1.eval("function f1() { debugger; evaluate('debugger', {newContext:true}) }");
+g2.eval("function f2() { f1(); assertEq(Number(this), 42) }");
+g2.f1 = g1.f1;
+
+var dbg = new Debugger(g1,g2);
+dbg.onDebuggerStatement = function(frame) {
+    var target = frame.older;
+    dbg.onDebuggerStatement = function(frame) {
+        assertEq(Number(target.this.unsafeDereference()), 42);
+    }
+}
+g2.f2.call(42);
diff --git a/js/src/jsdbgapi.cpp b/js/src/jsdbgapi.cpp
index 72a3c8af6c06..39ebeaa63c36 100644
--- a/js/src/jsdbgapi.cpp
+++ b/js/src/jsdbgapi.cpp
@@ -1061,7 +1061,7 @@ FormatFrame(JSContext *cx, const NonBuiltinScriptFrameIter &iter, char *buf, int
 
     RootedValue thisVal(cx);
     AutoPropertyDescArray thisProps(cx);
-    if (iter.computeThis()) {
+    if (iter.computeThis(cx)) {
         thisVal = iter.thisv();
         if (showThisProps && !thisVal.isPrimitive())
             thisProps.fetch(&thisVal.toObject());
diff --git a/js/src/vm/Debugger.cpp b/js/src/vm/Debugger.cpp
index 2daed0e2273b..70e089d14a0c 100644
--- a/js/src/vm/Debugger.cpp
+++ b/js/src/vm/Debugger.cpp
@@ -3820,7 +3820,7 @@ DebuggerFrame_getThis(JSContext *cx, unsigned argc, Value *vp)
     RootedValue thisv(cx);
     {
         AutoCompartment ac(cx, iter.scopeChain());
-        if (!iter.computeThis())
+        if (!iter.computeThis(cx))
             return false;
         thisv = iter.thisv();
     }
@@ -4220,7 +4220,7 @@ DebuggerGenericEval(JSContext *cx, const char *fullMethodName, const Value &code
     Rooted<Env *> env(cx);
     if (iter) {
         /* ExecuteInEnv requires 'fp' to have a computed 'this" value. */
-        if (!iter->computeThis())
+        if (!iter->computeThis(cx))
             return false;
         thisv = iter->thisv();
         env = GetDebugScopeForFrame(cx, iter->abstractFramePtr());
diff --git a/js/src/vm/Stack.cpp b/js/src/vm/Stack.cpp
index 4a36d5034418..dd65a048fbb2 100644
--- a/js/src/vm/Stack.cpp
+++ b/js/src/vm/Stack.cpp
@@ -1099,12 +1099,12 @@ ScriptFrameIter::argsObj() const
 }
 
 bool
-ScriptFrameIter::computeThis() const
+ScriptFrameIter::computeThis(JSContext *cx) const
 {
     JS_ASSERT(!done());
     if (!isIon()) {
-        JS_ASSERT(data_.cx_);
-        return ComputeThis(data_.cx_, abstractFramePtr());
+        assertSameCompartment(cx, scopeChain());
+        return ComputeThis(cx, abstractFramePtr());
     }
     return true;
 }
diff --git a/js/src/vm/Stack.h b/js/src/vm/Stack.h
index 0d30d0f02f00..ebbf73846dc7 100644
--- a/js/src/vm/Stack.h
+++ b/js/src/vm/Stack.h
@@ -1519,7 +1519,7 @@ class ScriptFrameIter
     ArgumentsObject &argsObj() const;
 
     // Ensure that thisv is correct, see ComputeThis.
-    bool        computeThis() const;
+    bool        computeThis(JSContext *cx) const;
     Value       thisv() const;
 
     Value       returnValue() const;