diff --git a/js/src/jit-test/tests/basic/bug657975.js b/js/src/jit-test/tests/basic/bug657975.js
new file mode 100644
index 00000000000..91cf383c223
--- /dev/null
+++ b/js/src/jit-test/tests/basic/bug657975.js
@@ -0,0 +1,8 @@
+// |jit-test| debug
+
+// bug 658491
+function f7() {
+  try { y = w; } catch(y) {}
+}
+trap(f7, 14, '')
+f7()
diff --git a/js/src/jsapi-tests/testDebugger.cpp b/js/src/jsapi-tests/testDebugger.cpp
index 91c88849185..75f0e2c398e 100644
--- a/js/src/jsapi-tests/testDebugger.cpp
+++ b/js/src/jsapi-tests/testDebugger.cpp
@@ -4,6 +4,7 @@
 
 #include "tests.h"
 #include "jsdbgapi.h"
+#include "jscntxt.h"
 
 static int callCount[2] = {0, 0};
 
@@ -252,3 +253,42 @@ bool testIndirectEval(JSObject *scope, JSObject *g, const char *code, int expect
     return true;
 }
 END_TEST(testDebugger_newScriptHook)
+
+BEGIN_TEST(testDebugger_singleStepThrow)
+    {
+        CHECK(JS_SetDebugModeForCompartment(cx, cx->compartment, true));
+        CHECK(JS_SetInterrupt(rt, onStep, NULL));
+
+        uint32 opts = JS_GetOptions(cx);
+        opts |= JSOPTION_METHODJIT | JSOPTION_METHODJIT_ALWAYS;
+        opts &= ~JSOPTION_JIT;
+        JS_SetOptions(cx, opts);
+
+        CHECK(JS_DefineFunction(cx, global, "setStepMode", setStepMode, 0, 0));
+        EXEC("var e;\n"
+             "setStepMode();\n"
+             "function f() { throw 0; }\n"
+             "try { f(); }\n"
+             "catch (x) { e = x; }\n");
+        return true;
+    }
+
+    static JSBool
+    setStepMode(JSContext *cx, uintN argc, jsval *vp)
+    {
+        JSStackFrame *fp = JS_GetScriptedCaller(cx, NULL);
+        JS_ASSERT(fp);
+        JSScript *script = JS_GetFrameScript(cx, fp);
+        JS_ASSERT(script);
+        if (!JS_SetSingleStepMode(cx, script, true))
+            return false;
+        JS_SET_RVAL(cx, vp, JSVAL_VOID);
+        return true;
+    }
+
+    static JSTrapStatus
+    onStep(JSContext *cx, JSScript *script, jsbytecode *pc, jsval *rval, void *closure)
+    {
+        return JSTRAP_CONTINUE;
+    }
+END_TEST(testDebugger_singleStepThrow)
diff --git a/js/src/methodjit/Compiler.cpp b/js/src/methodjit/Compiler.cpp
index 7f57a072e44..c7a1572a696 100644
--- a/js/src/methodjit/Compiler.cpp
+++ b/js/src/methodjit/Compiler.cpp
@@ -942,6 +942,17 @@ mjit::Compiler::generateMethod()
         SPEW_OPCODE();
         JS_ASSERT(frame.stackDepth() == opinfo->stackDepth);
 
+        // If this is an exception entry point, then jsl_InternalThrow has set
+        // VMFrame::fp to the correct fp for the entry point. We need to copy
+        // that value here to FpReg so that FpReg also has the correct sp.
+        // Otherwise, we would simply be using a stale FpReg value.
+        // Additionally, we check the interrupt flag to allow interrupting
+        // deeply nested exception handling.
+        if (op == JSOP_ENTERBLOCK && analysis->getCode(PC).exceptionEntry) {
+            restoreFrameRegs(masm);
+            interruptCheckHelper();
+        }
+
         if (trap) {
             prepareStubCall(Uses(0));
             masm.move(Imm32(trap), Registers::ArgReg1);
@@ -4831,17 +4842,6 @@ mjit::Compiler::jumpAndTrace(Jump j, jsbytecode *target, Jump *slow)
 void
 mjit::Compiler::enterBlock(JSObject *obj)
 {
-    // If this is an exception entry point, then jsl_InternalThrow has set
-    // VMFrame::fp to the correct fp for the entry point. We need to copy
-    // that value here to FpReg so that FpReg also has the correct sp.
-    // Otherwise, we would simply be using a stale FpReg value.
-    // Additionally, we check the interrupt flag to allow interrupting
-    // deeply nested exception handling.
-    if (analysis->getCode(PC).exceptionEntry) {
-        restoreFrameRegs(masm);
-        interruptCheckHelper();
-    }
-
     uint32 oldFrameDepth = frame.localSlots();
 
     /* For now, don't bother doing anything for this opcode. */