diff --git a/src/racket/src/jit.c b/src/racket/src/jit.c
index 05a3fa89e3..e3ffa81ca7 100644
--- a/src/racket/src/jit.c
+++ b/src/racket/src/jit.c
@@ -3312,7 +3312,7 @@ static void on_demand_generate_lambda(Scheme_Native_Closure *nc, int argc, Schem
   if (ndata->code != scheme_on_demand_jit_code)
     return;
 
-  ndata->arity_code = NULL; /* => in progress */
+  ndata->arity_code = sjc.in_progress_on_demand_jit_arity_code; /* => in progress */
 
   scheme_generate_one(NULL, do_generate_closure, &gdata, 1, data->name, ndata);
 
diff --git a/src/racket/src/jit.h b/src/racket/src/jit.h
index 5d0ae881f9..27753a79d2 100644
--- a/src/racket/src/jit.h
+++ b/src/racket/src/jit.h
@@ -227,7 +227,7 @@ struct scheme_jit_common_record {
   void *fxvector_ref_code, *fxvector_ref_check_index_code, *fxvector_set_code, *fxvector_set_check_index_code;
   void *struct_raw_ref_code, *struct_raw_set_code;
   void *syntax_e_code;
-  void *on_demand_jit_arity_code;
+  void *on_demand_jit_arity_code, *in_progress_on_demand_jit_arity_code;
   void *get_stack_pointer_code;
   void *stack_cache_pop_code;
   void *struct_pred_code, *struct_pred_multi_code;
diff --git a/src/racket/src/jitcall.c b/src/racket/src/jitcall.c
index 23762634c9..9fee1ee2d9 100644
--- a/src/racket/src/jitcall.c
+++ b/src/racket/src/jitcall.c
@@ -1454,7 +1454,7 @@ int scheme_generate_app(Scheme_App_Rec *app, Scheme_Object **alt_rands, int num_
             Scheme_Native_Closure *nc;
             nc = (Scheme_Native_Closure *)scheme_jit_closure((Scheme_Object *)data, NULL);
             if (nc->code->code == scheme_on_demand_jit_code) {
-              if (nc->code->arity_code) { /* i.e., not in progress */
+              if (nc->code->arity_code != sjc.in_progress_on_demand_jit_arity_code) {
                 scheme_on_demand_generate_lambda(nc, 0, NULL);
               }
             }
diff --git a/src/racket/src/jitcommon.c b/src/racket/src/jitcommon.c
index bcd89ad733..72987b7522 100644
--- a/src/racket/src/jitcommon.c
+++ b/src/racket/src/jitcommon.c
@@ -729,6 +729,12 @@ static int common2(mz_jit_state *jitter, void *_data)
   CHECK_LIMIT();
   scheme_jit_register_helper_func(jitter, scheme_on_demand_jit_code);
 
+  /* Used for the state of a function that is being JITted 
+     (for a kind of cycle detection) without breaking concurrent 
+     future threads that might try to call the function. */
+  sjc.in_progress_on_demand_jit_arity_code = jit_get_ip().ptr;
+  (void)jit_jmpi(sjc.on_demand_jit_arity_code);
+
   /* *** app_values_tail_slow_code *** */
   /* RELIES ON jit_prolog(NATIVE_ARG_COUNT) FROM ABOVE */
   /* Rator in V1, arguments are in thread's multiple-values cells. */