diff --git a/js-assembler/assemble-open-coded.rkt b/js-assembler/assemble-open-coded.rkt
index 57bc7e3..c8196bd 100644
--- a/js-assembler/assemble-open-coded.rkt
+++ b/js-assembler/assemble-open-coded.rkt
@@ -70,7 +70,7 @@
            (assemble-boolean-chain "plt.baselib.numbers.greaterThanOrEqual" checked-operands)]
           
           [(cons)
-           (format "RT.makePair(~a, ~a)"
+           (format "RT.makePair(~a,~a)"
                    (first checked-operands)
                    (second checked-operands))]
 
@@ -93,13 +93,13 @@
                    (first checked-operands))]
           
           [(null?)
-           (format "(~a === RT.NULL)" (first checked-operands))]
+           (format "(~a===RT.NULL)" (first checked-operands))]
 
           [(not)
-           (format "(~a === false)" (first checked-operands))]
+           (format "(~a=== alse)" (first checked-operands))]
           
           [(eq?)
-           (format "(~a === ~a)" (first checked-operands) (second checked-operands))])))
+           (format "(~a===~a)" (first checked-operands) (second checked-operands))])))
 
 
 
@@ -163,7 +163,7 @@
                             (format "RT.isPair")]
                            [(box)
                             (format "RT.isBox")])])
-           (format "RT.testArgument(M, ~s, ~a, ~a, ~a, ~s)"
+           (format "RT.testArgument(M,~s,~a,~a,~a,~s)"
                    (symbol->string domain)
                    predicate
                    operand-string
diff --git a/js-assembler/assemble.rkt b/js-assembler/assemble.rkt
index df19d39..283182d 100644
--- a/js-assembler/assemble.rkt
+++ b/js-assembler/assemble.rkt
@@ -180,15 +180,12 @@ EOF
 (: assemble-basic-block (BasicBlock Blockht (Setof Symbol) (Setof Symbol) Output-Port -> 'ok))
 (define (assemble-basic-block a-basic-block blockht entry-points function-entry-and-exit-names op)
   (match (BasicBlock-stmts a-basic-block)
-    ;; [(list (struct PopEnvironment (n (and (? (lambda (c) (equal? c (Const 0))))
-    ;;                                       skip)))
-    ;;        (struct GotoStatement ((and (? Label?)
-    ;;                                    target))))
-    ;;  (fprintf op "~a=RT.si_popgoto(~a,function(){return ~a});\n"
-    ;;           (assemble-label (make-Label (BasicBlock-name a-basic-block)))
-    ;;           (assemble-oparg n)
-    ;;           (assemble-label target))
-    ;;  'ok]
+    [(list (struct PerformStatement ((struct RaiseContextExpectedValuesError! (expected))))
+           stmts ...)
+     (fprintf op "~a=RT.si_context_expected(~a);\n"
+              (assemble-label (make-Label (BasicBlock-name a-basic-block)))
+              expected)
+     'ok]
     [else
      (default-assemble-basic-block a-basic-block blockht entry-points function-entry-and-exit-names op)]))
 
diff --git a/js-assembler/runtime-src/runtime.js b/js-assembler/runtime-src/runtime.js
index 3f1a97a..23097b4 100644
--- a/js-assembler/runtime-src/runtime.js
+++ b/js-assembler/runtime-src/runtime.js
@@ -668,15 +668,11 @@
 
     //////////////////////////////////////////////////////////////////////
     // Superinstructions to try to reduce code size.
-
-    var si_popgoto = function(n, gotoTargetThunk) {
-        return function(M) {
-            --M.cbt;
-            M.env.length-=n;
-            return gotoTargetThunk()(M);
-        };
+    var si_context_expected = function(n) {
+        if (n === 1) { return si_context_expected_1; }
+        return function(M) { raiseContextExpectedValuesError(M, n); }
     };
-
+    var si_context_expected_1 = function(M) { raiseContextExpectedValuesError(M, 1); }
 
 
 
@@ -815,7 +811,7 @@
     exports['getTracedAppKey'] = getTracedAppKey;
     exports['getTracedCalleeKey'] = getTracedCalleeKey;
 
-    exports['si_popgoto'] = si_popgoto;
+    exports['si_context_expected'] = si_context_expected;
     exports['checkClosureAndArity'] = checkClosureAndArity;