diff --git a/js-assembler/runtime-src/baselib-primitives.js b/js-assembler/runtime-src/baselib-primitives.js
index 793696c1..0f50647c 100644
--- a/js-assembler/runtime-src/baselib-primitives.js
+++ b/js-assembler/runtime-src/baselib-primitives.js
@@ -24,6 +24,7 @@
     var isNatural = baselib.numbers.isNatural;
     var isPair = baselib.lists.isPair;
     var isList = baselib.lists.isList;
+    var isVector = baselib.vectors.isVector;
     var isString = baselib.strings.isString;
     var isSymbol = baselib.symbols.isSymbol;
     var isBox = baselib.boxes.isBox;
@@ -658,6 +659,14 @@
         });
 
 
+    installPrimitiveProcedure(
+        'vector?',
+        1,
+        function (M) {
+            var firstArg = M.e[M.e.length-1];
+            return isVector(firstArg);
+        });
+
     installPrimitiveProcedure(
         'vector',
         baselib.arity.makeArityAtLeast(0),
diff --git a/tests/more-tests/sigs-cs019.expected b/tests/more-tests/sigs-cs019.expected
new file mode 100644
index 00000000..34f9d66e
--- /dev/null
+++ b/tests/more-tests/sigs-cs019.expected
@@ -0,0 +1,2 @@
+Running tests...
+All 37 tests passed!
diff --git a/tests/more-tests/sigs-cs019.rkt b/tests/more-tests/sigs-cs019.rkt
index 60089df7..4a467061 100755
--- a/tests/more-tests/sigs-cs019.rkt
+++ b/tests/more-tests/sigs-cs019.rkt
@@ -50,6 +50,7 @@
 (define: c1 : Char$ #\c)
 (check-expect c1 #\c)
 
+
 #;(define: key1 : Key$ "up")
 #;(check-expect key1 "up")
 
@@ -68,7 +69,10 @@
 (check-expect ((swf-f a-swf) 10) 11)
 #;(check-error (set-swf-f! a-swf 3))
 #;(check-violation-highlights 
+
+
  (set-swf-f! a-swf 3)
+
  ;; What should be highlighted is the entire signature
  (list "(Number$ -> Number$)")
  (list 26))
@@ -98,6 +102,8 @@
 (define mt$ (Sig: mt?))
 (define-struct: nd ([v : Number$] [l : Tree$] [r : Tree$]))
 
+
+
 #;(check-error (set-nd-v! (make-nd 0 (make-mt) (make-mt)) "x"))
 #;(check-violation-highlights
  (set-nd-v! (make-nd 0 (make-mt) (make-mt)) "x")
@@ -132,6 +138,7 @@
  (list 12))
 
 
+
 (define: (tree-sum (t : Tree$)) -> Number$
   (cond
     [(mt? t) 0]
@@ -151,6 +158,7 @@
  (list 14))
 
 
+
 (define: (prime? [n : (Sig: (lambda (n) (and (positive? n) (integer? n))))]) 
   -> Boolean$
   (local ([define (check k)
@@ -173,6 +181,8 @@
  (list "(Sig: (lambda (n) (and (positive? n) (integer? n))))")
  (list 22))
 
+
+
 (define BadSig$ (or: (Number$ -> Number$) Number$))
 ;(define: bs : BadSig 3)
 ;(define BadSig2 (not: (Number$ -> Number$)))
@@ -212,6 +222,8 @@
                             (list "Number$")
                             (list 27))
 
+
+
 (define: (i [f : (Number$ -> Number$)]) -> Number$
   (f 5))
 (check-expect (i add1) 6)
@@ -265,6 +277,8 @@
  (list "String$")
  (list 22))
 
+
+
 (check-expect (local ([define: (f [x : Number$]) -> String$
                         (number->string x)])
                 (f 10))
@@ -302,10 +316,13 @@
  (list 47))
 
 
+
+
 (define: l : (Listof: Number$) (list 1 2 3))
 (check-expect l (list 1 2 3))
 ; (define: m : (Listof: Number$) (list 1 2 "X"))
 
+
 (define: (n [l : (Listof: (Number$ -> Number$))]) -> (Listof: Number$)
   (map (lambda (f) (f 10)) l))
 (check-expect (n (list add1 sub1)) (list 11 9))
@@ -316,10 +333,13 @@
  (list 38))
 #;(check-error (n (list add1 string->number)))
 
+
 (define: vs : (Vectorof: String$)
   (vector "0" "1" "2"))
+
 (check-expect vs (vector "0" "1" "2"))
 
+
 (define: (cvts [ns : (Listof: Number$)]) -> (Listof: String$)
   (local [(define: cv : (Vectorof: ((Listof: String$) -> (Listof: String$)))
             (vector (lambda (cs) (cons "0" cs))
@@ -343,4 +363,4 @@
  (local [(define: v : S 4)]
    v)
  (list "2")
- (list 15))
\ No newline at end of file
+ (list 15))
diff --git a/tests/run-more-tests.rkt b/tests/run-more-tests.rkt
index 6a8838c3..ee05a853 100644
--- a/tests/run-more-tests.rkt
+++ b/tests/run-more-tests.rkt
@@ -36,4 +36,5 @@
 (test "more-tests/booleans-cs019.rkt")
 (test "more-tests/checking-cs019.rkt")
 (test "more-tests/sharing-cs019.rkt")
-(test "more-tests/basics-cs019.rkt")
\ No newline at end of file
+(test "more-tests/basics-cs019.rkt")
+(test "more-tests/sigs-cs019.rkt")