diff --git a/js-assembler/assemble-open-coded.rkt b/js-assembler/assemble-open-coded.rkt
index 208e6f6..1ec42dd 100644
--- a/js-assembler/assemble-open-coded.rkt
+++ b/js-assembler/assemble-open-coded.rkt
@@ -52,11 +52,21 @@
            (assemble-binop-chain "plt.baselib.numbers.divide" checked-operands)]
 
           [(add1)
-           (assemble-binop-chain "plt.baselib.numbers.add" (cons "1" checked-operands))]
+           (string-append
+            (format "(typeof(~a)==='number'&&(~a)<9E15?(~a)+1"
+                    (first operands) (first operands) (first operands))
+            ":"
+            (format "RT.checkedAdd1(M, ~a)" (first operands))
+            ")")]
+
           
           [(sub1)
-           (assemble-binop-chain "plt.baselib.numbers.subtract" (append checked-operands (list "1")))]
-
+           (string-append
+            (format "(typeof(~a)==='number'&&(~a)>-9E15?(~a)-1"
+                    (first operands) (first operands) (first operands))
+            ":"
+            (format "RT.checkedSub1(M, ~a)" (first operands))
+            ")")]
           [(<)
            (assemble-boolean-chain "plt.baselib.numbers.lessThan" checked-operands)]
 
diff --git a/js-assembler/runtime-src/runtime.js b/js-assembler/runtime-src/runtime.js
index 7c9d9fd..18255e6 100644
--- a/js-assembler/runtime-src/runtime.js
+++ b/js-assembler/runtime-src/runtime.js
@@ -804,6 +804,21 @@
     };
 
 
+    //////////////////////////////////////////////////////////////////////
+    var checkedAdd1 = function(M, n) {
+        return plt.baselib.numbers.add(
+            testArgument(M, 'number', isNumber, n, 0, 'add1'),
+            1);
+    };
+
+    var checkedSub1 = function(M, n) {
+        return plt.baselib.numbers.subtract(
+            testArgument(M, 'number', isNumber, n, 0, 'add1'),
+            1);
+    };
+
+
+
 
     //////////////////////////////////////////////////////////////////////
     //////////////////////////////////////////////////////////////////////
@@ -940,4 +955,6 @@
     exports['checkClosureAndArity'] = checkClosureAndArity;
     exports['checkPrimitiveArity'] = checkPrimitiveArity;
 
+    exports['checkedAdd1'] = checkedAdd1;
+    exports['checkedSub1'] = checkedSub1;
 }(this.plt, this.plt.baselib));
\ No newline at end of file
diff --git a/version.rkt b/version.rkt
index 077c809..4d46da8 100644
--- a/version.rkt
+++ b/version.rkt
@@ -7,4 +7,4 @@
 (provide version)
 (: version String)
 
-(define version "1.133")
+(define version "1.135")