diff --git a/hphp/runtime/vm/bytecode.cpp b/hphp/runtime/vm/bytecode.cpp
index 5fb5c0676..87e5bc8f9 100644
--- a/hphp/runtime/vm/bytecode.cpp
+++ b/hphp/runtime/vm/bytecode.cpp
@@ -1508,10 +1508,15 @@ void VMExecutionContext::syncGdbState() {
   }
 }
 
+static bool jitIsEnabled(const Unit* unit) {
+  if (!ThreadInfo::s_threadInfo->m_reqInjectionData.getJit()) return false;
+  return unit == nullptr || !unit->isInterpretOnly();
+}
+
 void VMExecutionContext::enterVMPrologue(ActRec* enterFnAr) {
   assert(enterFnAr);
   Stats::inc(Stats::VMEnter);
-  if (ThreadInfo::s_threadInfo->m_reqInjectionData.getJit()) {
+  if (jitIsEnabled(enterFnAr->m_func->unit())) {
     int np = enterFnAr->m_func->numParams();
     int na = enterFnAr->numArgs();
     if (na > np) na = np + 1;
@@ -1532,7 +1537,7 @@ void VMExecutionContext::enterVMWork(ActRec* enterFnAr) {
     start = enterFnAr->m_func->getFuncBody();
   }
   Stats::inc(Stats::VMEnter);
-  if (ThreadInfo::s_threadInfo->m_reqInjectionData.getJit()) {
+  if (jitIsEnabled(m_fp->unit())) {
     (void) m_fp->unit()->offsetOf(m_pc); /* assert */
     if (enterFnAr) {
       assert(start);
@@ -2570,12 +2575,14 @@ void VMExecutionContext::evalPHPDebugger(TypedValue* retval, StringData *code,
                                          int frame) {
   assert(retval);
   // The code has "<?php" prepended already
-  Unit* unit = compileEvalString(code);
+  Unit* unit = compile_string(code->data(), code->size());
   if (unit == nullptr) {
     raise_error("Syntax error");
     tvWriteNull(retval);
     return;
   }
+  // Do not JIT this unit, we are using it exactly once.
+  unit->setInterpretOnly();
 
   VarEnv *varEnv = nullptr;
   ActRec *fp = getFP();
diff --git a/hphp/runtime/vm/unit.h b/hphp/runtime/vm/unit.h
index 435964ae1..3aa9a40a4 100644
--- a/hphp/runtime/vm/unit.h
+++ b/hphp/runtime/vm/unit.h
@@ -643,6 +643,8 @@ public:
     m_cacheOffset = id >> 3;
     m_cacheMask = 1 << (id & 7);
   }
+  bool isInterpretOnly() const { return m_interpretOnly; }
+  void setInterpretOnly() { m_interpretOnly = false; }
   bool isMergeOnly() const { return m_mergeOnly; }
   void clearMergeOnly() { m_mergeOnly = false; }
   bool isEmpty() const { return m_mergeState & UnitMergeStateEmpty; }
@@ -714,6 +716,7 @@ private:
   uint8_t m_mergeState;
   uint8_t m_cacheMask;
   bool m_mergeOnly;
+  bool m_interpretOnly;
   LineTable m_lineTable;
   FuncTable m_funcTable;
   mutable PseudoMainCacheMap *m_pseudoMainCache;
diff --git a/hphp/test/quick/debugger/eval2.php b/hphp/test/quick/debugger/eval2.php
new file mode 100644
index 000000000..2e8f8342c
--- /dev/null
+++ b/hphp/test/quick/debugger/eval2.php
@@ -0,0 +1,5 @@
+<?php
+  function foo($x) {
+    return $x + 1;
+  }
+
diff --git a/hphp/test/quick/debugger/eval2.php.expectf b/hphp/test/quick/debugger/eval2.php.expectf
new file mode 100644
index 000000000..aea0975fc
--- /dev/null
+++ b/hphp/test/quick/debugger/eval2.php.expectf
@@ -0,0 +1,20 @@
+Program %s/eval2.php loaded. Type '[r]un' or '[c]ontinue' to go.
+b foo()
+Breakpoint 1 set upon entering foo()
+But wont break until function foo has been loaded.
+c
+Program %s/eval2.php exited normally.
+@ foo(1)
+Breakpoint 1 reached at foo() on line 3 of %s/eval2.php
+   2   function foo($x) {
+   3     return $x + 1;
+   4   }
+
+= $x
+1
+c
+= $x
+HipHop Notice: Undefined variable: x
+null
+
+quit
diff --git a/hphp/test/quick/debugger/eval2.php.in b/hphp/test/quick/debugger/eval2.php.in
new file mode 100644
index 000000000..43585a69e
--- /dev/null
+++ b/hphp/test/quick/debugger/eval2.php.in
@@ -0,0 +1,7 @@
+b foo()
+c
+@ foo(1)
+= $x
+c
+= $x
+