diff --git a/assemble.rkt b/assemble.rkt
index fa63f3e..315be00 100644
--- a/assemble.rkt
+++ b/assemble.rkt
@@ -233,6 +233,10 @@ EOF
       [(InstallContinuationMarkEntry!? op)
        empty]
       [(RaiseContextExpectedValuesError!? op)
+       empty]
+      [(RaiseArityMismatchError!? op)
+       empty]
+      [(RaiseOperatorApplicationError!? op)
        empty]))
   
   (unique/eq?
diff --git a/simulator.rkt b/simulator.rkt
index 6de51f7..399684c 100644
--- a/simulator.rkt
+++ b/simulator.rkt
@@ -388,7 +388,15 @@
            (error "context expected ~a values, received ~a values."
                   (RaiseContextExpectedValuesError!-expected op)
                   (machine-argcount m))]
-          )))
+
+	  [(RaiseArityMismatchError!? op)
+	   (error "expects ~s arguments, given ~a"
+		  (RaiseArityMismatchError!-expected op)
+		  (evaluate-oparg m (RaiseArityMismatchError!-received op)))]
+
+	  [(RaiseOperatorApplicationError!? op)
+	   (error "expected procedure, given ~a"
+		  (evaluate-oparg m (RaiseOperatorApplicationError!-operator op)))])))