diff --git a/include/cyclone/runtime.h b/include/cyclone/runtime.h
index d575e26e..5511f941 100644
--- a/include/cyclone/runtime.h
+++ b/include/cyclone/runtime.h
@@ -73,6 +73,7 @@ void gc_init_heap(long heap_size);
 #define Cyc_check_pair(d,obj) Cyc_check_type(d,Cyc_is_pair, pair_tag, obj);
 #define Cyc_check_proc(d,obj) Cyc_check_type2(d,Cyc_is_procedure, closureN_tag, obj);
 #define Cyc_check_num(d,obj) Cyc_check_type(d,Cyc_is_number, integer_tag, obj);
+#define Cyc_check_fixnum(d,obj) Cyc_check_type(d,Cyc_is_fixnum, integer_tag, obj);
 #define Cyc_check_int(d,obj) Cyc_check_type(d,Cyc_is_integer, integer_tag, obj);
 #define Cyc_check_str(d,obj) Cyc_check_type(d,Cyc_is_string, string_tag, obj);
 #define Cyc_check_sym(d,obj) Cyc_check_type(d,Cyc_is_symbol, symbol_tag, obj);
@@ -359,6 +360,7 @@ object Cyc_is_null(object o);
 object Cyc_is_number(object o);
 object Cyc_is_real(object o);
 object Cyc_is_integer(object o);
+object Cyc_is_fixnum(object o);
 object Cyc_is_bignum(object o);
 object Cyc_is_vector(object o);
 object Cyc_is_bytevector(object o);
diff --git a/runtime.c b/runtime.c
index bd811299..f73eefc9 100644
--- a/runtime.c
+++ b/runtime.c
@@ -1465,6 +1465,13 @@ object Cyc_is_real(object o)
   return Cyc_is_number(o);
 }
 
+object Cyc_is_fixnum(object o)
+{
+  if (obj_is_int(o))
+    return boolean_t;
+  return boolean_f;
+}
+
 object Cyc_is_integer(object o)
 {
   if ((o != NULL) && (obj_is_int(o) ||