diff --git a/js-assembler/runtime-src/baselib-exceptions.js b/js-assembler/runtime-src/baselib-exceptions.js
index 91dd3ee..1116475 100644
--- a/js-assembler/runtime-src/baselib-exceptions.js
+++ b/js-assembler/runtime-src/baselib-exceptions.js
@@ -98,14 +98,24 @@
                                           expectedTypeName,
                                           argumentOffset,
                                           actualValue) {
-	raise(MACHINE,
-              new Error(
-		  plt.baselib.format.format(
-		      "~a: expected ~a as argument ~e but received ~e",
-		      [callerName,
-		       expectedTypeName,
-		       (argumentOffset + 1),
-		       actualValue])));
+        if (argumentOffset !== undefined) {
+	    raise(MACHINE,
+                  new Error(
+		      plt.baselib.format.format(
+		          "~a: expected ~a as argument ~e but received ~e",
+		          [callerName,
+		           expectedTypeName,
+		           (argumentOffset + 1),
+		           actualValue])));
+        } else {
+	    raise(MACHINE,
+                  new Error(
+		      plt.baselib.format.format(
+		          "~a: expected ~a but received ~e",
+		          [callerName,
+		           expectedTypeName,
+		           actualValue])));
+        }
     };
 
     var raiseContextExpectedValuesError = function(MACHINE, expected) {
diff --git a/js-assembler/runtime-src/runtime.js b/js-assembler/runtime-src/runtime.js
index add453f..56a3abd 100644
--- a/js-assembler/runtime-src/runtime.js
+++ b/js-assembler/runtime-src/runtime.js
@@ -883,6 +883,15 @@ if(this['plt'] === undefined) { this['plt'] = {}; }
 	    return isPair(firstArg);
         });
 
+
+    installPrimitiveProcedure(
+        'list?',
+        1,
+        function(MACHINE) {
+            return isList(MACHINE.env[MACHINE.env.length -1]);
+        });
+
+
     installPrimitiveProcedure(
         'set-car!',
         2,
@@ -1581,8 +1590,69 @@ if(this['plt'] === undefined) { this['plt'] = {}; }
         });
 
 
+
+    installPrimitiveProcedure(
+        'error',
+        plt.baselib.arity.makeArityAtLeast(1),
+        function(MACHINE) {
+            if (MACHINE.argcount === 1) {
+                var sym = checkSymbol(MACHINE, 'error', 1);
+                // FIXME: we should collect the current continuation marks here...
+                raise(MACHINE, plt.baselib.exceptions.makeExnFail(String(sym), undefined));
+            } 
+            
+            if (isString(MACHINE.env[MACHINE.env.length - 1])) {
+                var vs = [];
+                for (var i = 1; i < MACHINE.argcount; i++) {
+                    vs.push(plt.baselib.format.format("~e", [MACHINE.env[MACHINE.env.length - 1 - i]]));
+                }
+                raise(MACHINE, plt.baselib.exceptions.makeExnFail(String(MACHINE.env[MACHINE.env.length - 1]) +
+                                           ": " +
+                                           vs.join(' '),
+                                          undefined));
+            }
+
+            if (isSymbol(MACHINE.env[MACHINE.env.length - 1])) {
+                var fmtString = checkString(MACHINE, 'error', 1);
+                var args = [MACHINE.env[MACHINE.env.length - 1]];
+                for (i = 2; i < MACHINE.argcount; i++) {
+                    args.push(MACHINE.env[MACHINE.env.length - 1 - i]);
+                }
+                raise(MACHINE, plt.baselib.exceptions.makeExnFail(
+                    plt.baselib.format.format('~s: ' + String(fmtString),
+                                              args),
+                                           undefined));
+            }
+
+            // Fall-through
+            raiseArgumentTypeError(MACHINE, 'error', 'symbol or string', 0, MACHINE.env[MACHINE.env.length - 1]);
+        });
+
+
+    installPrimitiveProcedure(
+        'raise-type-error',
+        plt.baselib.arity.makeArityAtLeast(3),
+        function(MACHINE) {
+            var name = checkSymbol(MACHINE, 'raise-type-error', 0);
+            var expected = checkString(MACHINE, 'raise-type-error', 1);
+            if (MACHINE.argcount === 3) {
+                raiseArgumentTypeError(MACHINE, 
+                                       name,
+                                       expected,
+                                       undefined,
+                                       MACHINE.env[MACHINE.env.length - 1 - 2]);
+            } else {
+                raiseArgumentTypeError(MACHINE, 
+                                       name,
+                                       expected,
+                                       checkNatural(MACHINE, 'raise-type-error', 2),
+                                       MACHINE.env[MACHINE.env.length - 1 - 2]);
+            }
+        });
     
 
+
+
     installPrimitiveClosure(
         'make-struct-type',
         makeList(4, 5, 6, 7, 8, 9, 10, 11),
diff --git a/lang/kernel.rkt b/lang/kernel.rkt
index b94569d..d8b3708 100644
--- a/lang/kernel.rkt
+++ b/lang/kernel.rkt
@@ -192,6 +192,7 @@
 ;;  (identity -identity)
 ;;  raise
 error
+raise-type-error
 
 ;;  make-exn
 ;;  make-exn:fail
@@ -251,7 +252,8 @@ error
   string->number
 ;;  procedure?
   pair?
-;;  (undefined? -undefined?)
+  list?
+  ;;  (undefined? -undefined?)
 ;;  immutable?
 ;;  void?
 symbol?
@@ -293,7 +295,6 @@ exact?
 ;;  cdddr
 ;;  cadddr
   length
-;;  list?
 ;;  list*
   list-ref
 ;;  list-tail