diff --git a/racket/src/racket/src/fun.c b/racket/src/racket/src/fun.c
index 0c38151030..b1aff09b65 100644
--- a/racket/src/racket/src/fun.c
+++ b/racket/src/racket/src/fun.c
@@ -3377,7 +3377,8 @@ static Scheme_Object *procedure_equal_closure_p(int argc, Scheme_Object *argv[])
       Scheme_Native_Closure *c1 = (Scheme_Native_Closure *)v1;
       Scheme_Native_Closure *c2 = (Scheme_Native_Closure *)v2;
 
-      if (SAME_OBJ(c1->code, c2->code)) {
+      if (SAME_OBJ(c1->code, c2->code)
+          || (c1->code->eq_key && SAME_OBJ(c1->code->eq_key, c2->code->eq_key))) {
 	int i;
 	i = c1->code->closure_size;
 	if (i < 0) {
@@ -3442,6 +3443,11 @@ static Scheme_Object *procedure_specialize(int argc, Scheme_Object *argv[])
     if ((nc->code->start_code == scheme_on_demand_jit_code)
         && !(SCHEME_NATIVE_CLOSURE_DATA_FLAGS(nc->code) & NATIVE_SPECIALIZED)) {
       Scheme_Native_Closure_Data *data;
+      if (!nc->code->eq_key) {
+        void *p;
+        p = scheme_malloc_atomic(sizeof(int));
+        nc->code->eq_key = p;
+      }
       data = MALLOC_ONE_TAGGED(Scheme_Native_Closure_Data);
       memcpy(data, nc->code, sizeof(Scheme_Native_Closure_Data));
       SCHEME_NATIVE_CLOSURE_DATA_FLAGS(data) |= NATIVE_SPECIALIZED;
diff --git a/racket/src/racket/src/mzmark_jit.inc b/racket/src/racket/src/mzmark_jit.inc
index a6cbabd86d..aeb5be06da 100644
--- a/racket/src/racket/src/mzmark_jit.inc
+++ b/racket/src/racket/src/mzmark_jit.inc
@@ -158,6 +158,7 @@ static int native_unclosed_proc_MARK(void *p, struct NewGC *gc) {
     gcMARK2(d->u.arities, gc);
   }
   gcMARK2(d->tl_map, gc);
+  gcMARK2(d->eq_key, gc);
 
 # ifdef GC_NO_SIZE_NEEDED_FROM_PROCS
   return 0;
@@ -183,6 +184,7 @@ static int native_unclosed_proc_FIXUP(void *p, struct NewGC *gc) {
     gcFIXUP2(d->u.arities, gc);
   }
   gcFIXUP2(d->tl_map, gc);
+  gcFIXUP2(d->eq_key, gc);
 
 # ifdef GC_NO_SIZE_NEEDED_FROM_PROCS
   return 0;
diff --git a/racket/src/racket/src/mzmarksrc.c b/racket/src/racket/src/mzmarksrc.c
index 96d438a8df..d099050a6d 100644
--- a/racket/src/racket/src/mzmarksrc.c
+++ b/racket/src/racket/src/mzmarksrc.c
@@ -2511,6 +2511,7 @@ native_unclosed_proc {
     gcMARK2(d->u.arities, gc);
   }
   gcMARK2(d->tl_map, gc);
+  gcMARK2(d->eq_key, gc);
 
  size:
   gcBYTES_TO_WORDS(sizeof(Scheme_Native_Closure_Data));
diff --git a/racket/src/racket/src/schpriv.h b/racket/src/racket/src/schpriv.h
index b76978cd72..f1ea327d3a 100644
--- a/racket/src/racket/src/schpriv.h
+++ b/racket/src/racket/src/schpriv.h
@@ -2784,6 +2784,7 @@ typedef struct Scheme_Native_Closure_Data {
   /* Thumb code is off by one, need real start for GC */
   void *retain_code;
 #endif
+  void *eq_key; /* for `procedure-closure-contents-eq?` */
 } Scheme_Native_Closure_Data;
 
 #define SCHEME_NATIVE_CLOSURE_DATA_FLAGS(obj) MZ_OPT_HASH_KEY(&(obj)->iso)