diff --git a/hoax/compile-ops.rkt b/hoax/compile-ops.rkt
index 8657643..138c4d1 100644
--- a/hoax/compile-ops.rkt
+++ b/hoax/compile-ops.rkt
@@ -161,6 +161,7 @@
            (theend (gensym 'theend)))
        (seq (Pop r8)
             (assert-natural r8)
+            (assert-char rax)
 
             ; special case for length = 0
             (Cmp r8 0)
diff --git a/hoax/test/test-runner.rkt b/hoax/test/test-runner.rkt
index 9f1053a..29eff4b 100644
--- a/hoax/test/test-runner.rkt
+++ b/hoax/test/test-runner.rkt
@@ -143,6 +143,7 @@
     (check-equal? (run '"") "")
     (check-equal? (run '"fred") "fred")
     (check-equal? (run '"wilma") "wilma")
+    (check-equal? (run '(make-string 0 #t)) 'err)
     (check-equal? (run '(make-string 0 #\f)) "")
     (check-equal? (run '(make-string 3 #\f)) "fff")
     (check-equal? (run '(make-string 3 #\g)) "ggg")
diff --git a/iniquity/compile-ops.rkt b/iniquity/compile-ops.rkt
index 8657643..138c4d1 100644
--- a/iniquity/compile-ops.rkt
+++ b/iniquity/compile-ops.rkt
@@ -161,6 +161,7 @@
            (theend (gensym 'theend)))
        (seq (Pop r8)
             (assert-natural r8)
+            (assert-char rax)
 
             ; special case for length = 0
             (Cmp r8 0)
diff --git a/iniquity/test/parse.rkt b/iniquity/test/parse.rkt
index fd413ee..ea9197b 100644
--- a/iniquity/test/parse.rkt
+++ b/iniquity/test/parse.rkt
@@ -47,6 +47,7 @@
   (check-equal? (parse "asdf") (p (Lit "asdf")))
   (check-equal? (parse '(make-string 10 #\a))
                 (p (Prim2 'make-string (Lit 10) (Lit #\a)))))
+  
 (begin ; Iniquity
   (check-equal? (parse '(define (f x) x) 1)
                 (Prog (list (Defn 'f '(x) (Var 'x))) (Lit 1)))
diff --git a/iniquity/test/test-runner.rkt b/iniquity/test/test-runner.rkt
index 6e4acb5..558308f 100644
--- a/iniquity/test/test-runner.rkt
+++ b/iniquity/test/test-runner.rkt
@@ -143,6 +143,7 @@
     (check-equal? (run '"") "")
     (check-equal? (run '"fred") "fred")
     (check-equal? (run '"wilma") "wilma")
+    (check-equal? (run '(make-string 0 #t)) 'err)
     (check-equal? (run '(make-string 0 #\f)) "")
     (check-equal? (run '(make-string 3 #\f)) "fff")
     (check-equal? (run '(make-string 3 #\g)) "ggg")
diff --git a/jig/compile-ops.rkt b/jig/compile-ops.rkt
index 8657643..138c4d1 100644
--- a/jig/compile-ops.rkt
+++ b/jig/compile-ops.rkt
@@ -161,6 +161,7 @@
            (theend (gensym 'theend)))
        (seq (Pop r8)
             (assert-natural r8)
+            (assert-char rax)
 
             ; special case for length = 0
             (Cmp r8 0)
diff --git a/jig/test/test-runner.rkt b/jig/test/test-runner.rkt
index 6e4acb5..558308f 100644
--- a/jig/test/test-runner.rkt
+++ b/jig/test/test-runner.rkt
@@ -143,6 +143,7 @@
     (check-equal? (run '"") "")
     (check-equal? (run '"fred") "fred")
     (check-equal? (run '"wilma") "wilma")
+    (check-equal? (run '(make-string 0 #t)) 'err)
     (check-equal? (run '(make-string 0 #\f)) "")
     (check-equal? (run '(make-string 3 #\f)) "fff")
     (check-equal? (run '(make-string 3 #\g)) "ggg")
diff --git a/knock/compile-ops.rkt b/knock/compile-ops.rkt
index 8657643..138c4d1 100644
--- a/knock/compile-ops.rkt
+++ b/knock/compile-ops.rkt
@@ -161,6 +161,7 @@
            (theend (gensym 'theend)))
        (seq (Pop r8)
             (assert-natural r8)
+            (assert-char rax)
 
             ; special case for length = 0
             (Cmp r8 0)
diff --git a/knock/test/test-runner.rkt b/knock/test/test-runner.rkt
index a7c0fef..68306a3 100644
--- a/knock/test/test-runner.rkt
+++ b/knock/test/test-runner.rkt
@@ -143,6 +143,7 @@
     (check-equal? (run '"") "")
     (check-equal? (run '"fred") "fred")
     (check-equal? (run '"wilma") "wilma")
+    (check-equal? (run '(make-string 0 #t)) 'err)
     (check-equal? (run '(make-string 0 #\f)) "")
     (check-equal? (run '(make-string 3 #\f)) "fff")
     (check-equal? (run '(make-string 3 #\g)) "ggg")
diff --git a/loot/compile-ops.rkt b/loot/compile-ops.rkt
index 63090ff..14ae7d9 100644
--- a/loot/compile-ops.rkt
+++ b/loot/compile-ops.rkt
@@ -161,6 +161,7 @@
            (theend (gensym 'theend)))
        (seq (Pop r8)
             (assert-natural r8)
+            (assert-char rax)
 
             ; special case for length = 0
             (Cmp r8 0)
diff --git a/loot/test/test-runner.rkt b/loot/test/test-runner.rkt
index 9d32fe3..d5ecf65 100644
--- a/loot/test/test-runner.rkt
+++ b/loot/test/test-runner.rkt
@@ -143,6 +143,7 @@
     (check-equal? (run '"") "")
     (check-equal? (run '"fred") "fred")
     (check-equal? (run '"wilma") "wilma")
+    (check-equal? (run '(make-string 0 #t)) 'err)
     (check-equal? (run '(make-string 0 #\f)) "")
     (check-equal? (run '(make-string 3 #\f)) "fff")
     (check-equal? (run '(make-string 3 #\g)) "ggg")