diff --git a/include/chibi/features.h b/include/chibi/features.h
index 2a90172c..ceae2b46 100644
--- a/include/chibi/features.h
+++ b/include/chibi/features.h
@@ -787,6 +787,10 @@
 #define SEXP_MAX_STACK_SIZE SEXP_INIT_STACK_SIZE*1000
 #endif
 
+#ifndef SEXP_MAX_VECTOR_LENGTH
+#define SEXP_MAX_VECTOR_LENGTH (SEXP_MAX_FIXNUM >> 1)
+#endif
+
 #ifndef SEXP_DEFAULT_EQUAL_DEPTH
 #define SEXP_DEFAULT_EQUAL_DEPTH 10000
 #endif
diff --git a/sexp.c b/sexp.c
index 63353867..5ce4eb68 100644
--- a/sexp.c
+++ b/sexp.c
@@ -1524,8 +1524,10 @@ sexp sexp_string_to_symbol_op (sexp ctx, sexp self, sexp_sint_t n, sexp str) {
 
 sexp sexp_make_vector_op (sexp ctx, sexp self, sexp_sint_t n, sexp len, sexp dflt) {
   sexp vec, *x;
-  int i, clen = sexp_unbox_fixnum(len);
+  sexp_sint_t i, clen = sexp_unbox_fixnum(len);
   if (! clen) return sexp_global(ctx, SEXP_G_EMPTY_VECTOR);
+  if (clen < 0 || clen > SEXP_MAX_VECTOR_LENGTH)
+    return sexp_xtype_exception(ctx, self, "vector length out of range", len);
   vec = sexp_alloc_tagged(ctx, sexp_sizeof(vector) + clen*sizeof(sexp),
                           SEXP_VECTOR);
   if (sexp_exceptionp(vec)) return vec;