diff --git a/srfi/143.sld b/srfi/143.sld
index 21c31256..18d77360 100644
--- a/srfi/143.sld
+++ b/srfi/143.sld
@@ -17,7 +17,8 @@
     ;fxzero? fxpositive? fxnegative? fxodd? fxeven?
     ;fx= fx< fx> fx<= fx>=
     ;fxmax fxmin
-    ;fx+ fx- fx*
+    fx+
+    ;fx- fx*
     ;fxabs fxsquare fxsqrt fxexpt
     ;fx+/carry
     ;fx-/carry
@@ -51,6 +52,13 @@
     ;fxfold fxfor-each fxunfold
     ;fxlogical-shift
   )
+  (inline
+    fx-width
+    fx-greatest
+    fx-least
+    fixnum?
+    fx+
+  )
   (begin
     (define (fx-width) 31)
     (define (fx-greatest) 1073741823)
@@ -59,5 +67,11 @@
       "(void *data, int argc, closure _, object k, object obj)"
       " return_closcall1(data, k, 
           obj_is_int(obj) ? boolean_t : boolean_f); ")
+    (define-c fx+
+      "(void *data, int argc, closure _, object k, object i, object j)"
+      " Cyc_check_fixnum(data, i);
+        Cyc_check_fixnum(data, j);
+        object result = obj_int2obj(obj_obj2int(i) + obj_obj2int(j));
+        return_closcall1(data, k, result); ")
   ))