diff --git a/pkgs/racket-test-core/tests/racket/optimize.rktl b/pkgs/racket-test-core/tests/racket/optimize.rktl
index 9495f762b3..7fabaa0b49 100644
--- a/pkgs/racket-test-core/tests/racket/optimize.rktl
+++ b/pkgs/racket-test-core/tests/racket/optimize.rktl
@@ -610,6 +610,17 @@
 (test-comp '(lambda (z) (let ([f (lambda (i) (car i))]) (f z)) #t)
            '(lambda (z) (let ([f (lambda (i) (car i))]) (f z)) (pair? z)))
 
+(test-comp '(lambda (z) (fl+ z z))
+           '(lambda (z) (real->double-flonum (fl+ z z))))
+(test-comp '(lambda (z) (fl+ z z))
+           '(lambda (z) (exact->inexact (fl+ z z))))
+(test-comp '(lambda (z) (real->double-flonum z))
+           '(lambda (z) (real->double-flonum (real->double-flonum z))))
+(test-comp '(lambda (z) (unsafe-fx->fl (fx+ z z)))
+           '(lambda (z) (real->double-flonum (fx+ z z))))
+(test-comp '(lambda (z) (unsafe-fx->fl (fx+ z z)))
+           '(lambda (z) (exact->inexact (fx+ z z))))
+
 ; Test that the optimizer infers correctly the type of all the arguments
 ; and the type of the return value. Use #f in case the type is unknown.
 (define (test-arg-types proc/args? val? 
diff --git a/racket/src/racket/src/number.c b/racket/src/racket/src/number.c
index e66c8034ca..a54d58a5c5 100644
--- a/racket/src/racket/src/number.c
+++ b/racket/src/racket/src/number.c
@@ -211,6 +211,7 @@ READ_ONLY Scheme_Object *scheme_unsafe_fxand_proc;
 READ_ONLY Scheme_Object *scheme_unsafe_fxior_proc;
 READ_ONLY Scheme_Object *scheme_unsafe_fxxor_proc;
 READ_ONLY Scheme_Object *scheme_unsafe_fxrshift_proc;
+READ_ONLY Scheme_Object *scheme_unsafe_fx_to_fl_proc;
 
 READ_ONLY double scheme_infinity_val;
 READ_ONLY double scheme_minus_infinity_val;
@@ -536,6 +537,8 @@ scheme_init_number (Scheme_Startup_Env *env)
     flags = SCHEME_PRIM_IS_UNARY_INLINED;
   else
     flags = SCHEME_PRIM_SOMETIMES_INLINED;
+  flags |= (SCHEME_PRIM_PRODUCES_FLONUM
+            | SCHEME_PRIM_AD_HOC_OPT);
   SCHEME_PRIM_PROC_FLAGS(p) |= scheme_intern_prim_opt_flags(flags);
   scheme_addto_prim_instance("real->double-flonum", p, env);
 
@@ -735,6 +738,7 @@ scheme_init_number (Scheme_Startup_Env *env)
     flags = SCHEME_PRIM_IS_UNARY_INLINED;
   else
     flags = SCHEME_PRIM_SOMETIMES_INLINED;
+  flags |= SCHEME_PRIM_AD_HOC_OPT;
   SCHEME_PRIM_PROC_FLAGS(p) |= scheme_intern_prim_opt_flags(flags);
   scheme_addto_prim_instance("exact->inexact", p, env);
 
@@ -1370,6 +1374,8 @@ void scheme_init_unsafe_number(Scheme_Startup_Env *env)
                                                             | SCHEME_PRIM_IS_UNSAFE_FUNCTIONAL
                                                             | SCHEME_PRIM_PRODUCES_FLONUM);
   scheme_addto_prim_instance("unsafe-fx->fl", p, env);
+  REGISTER_SO(scheme_unsafe_fx_to_fl_proc);
+  scheme_unsafe_fx_to_fl_proc = p;
 
   p = scheme_make_folding_prim(unsafe_fl_to_fx, "unsafe-fl->fx", 1, 1, 1);
   SCHEME_PRIM_PROC_FLAGS(p) |= scheme_intern_prim_opt_flags(SCHEME_PRIM_IS_UNARY_INLINED
diff --git a/racket/src/racket/src/optimize.c b/racket/src/racket/src/optimize.c
index 83cd57c5ff..bb7cc87b1e 100644
--- a/racket/src/racket/src/optimize.c
+++ b/racket/src/racket/src/optimize.c
@@ -4586,7 +4586,7 @@ static Scheme_Object *finish_optimize_application2(Scheme_App2_Rec *app, Optimiz
         && !strcmp(SCHEME_SYM_VAL(rand), "vm")) {
       /* For the expander's benefit, optimize `(system-type 'vm)` to `'racket`
          to effectively select backend details statically. */
-      return scheme_intern_symbol("racket");
+      return replace_tail_inside(scheme_intern_symbol("racket"), inside, app->rand);
     }
 
     {
@@ -4630,6 +4630,16 @@ static Scheme_Object *finish_optimize_application2(Scheme_App2_Rec *app, Optimiz
         check_known(info, app_o, rator, rand, "keyword->string", scheme_keyword_p_proc, scheme_true, info->unsafe_mode);
 
         check_known(info, app_o, rator, rand, "char->integer", scheme_char_p_proc, scheme_unsafe_char_to_integer_proc, info->unsafe_mode);
+
+        if (IS_NAMED_PRIM(rator, "real->double-flonum")
+            || IS_NAMED_PRIM(rator, "exact->inexact")) {
+          Scheme_Object *pred;
+          pred = expr_implies_predicate(rand, info);
+          if (predicate_implies(pred, scheme_flonum_p_proc))
+            return replace_tail_inside(rand, inside, rand);
+          else if (predicate_implies(pred, scheme_fixnum_p_proc))
+            reset_rator(app_o, scheme_unsafe_fx_to_fl_proc);
+        }
       }
       
       if (SCHEME_PRIM_PROC_OPT_FLAGS(rator) & SCHEME_PRIM_WANTS_REAL)
diff --git a/racket/src/racket/src/schpriv.h b/racket/src/racket/src/schpriv.h
index 6295d09717..ede70cd2f2 100644
--- a/racket/src/racket/src/schpriv.h
+++ b/racket/src/racket/src/schpriv.h
@@ -591,6 +591,7 @@ extern Scheme_Object *scheme_unsafe_fxand_proc;
 extern Scheme_Object *scheme_unsafe_fxior_proc;
 extern Scheme_Object *scheme_unsafe_fxxor_proc;
 extern Scheme_Object *scheme_unsafe_fxrshift_proc;
+extern Scheme_Object *scheme_unsafe_fx_to_fl_proc;
 extern Scheme_Object *scheme_unsafe_pure_proc;
 
 extern Scheme_Object *scheme_string_p_proc;