diff --git a/include/chibi/sexp.h b/include/chibi/sexp.h
index 32b7c1c5..dbb20384 100755
--- a/include/chibi/sexp.h
+++ b/include/chibi/sexp.h
@@ -1198,6 +1198,8 @@ SEXP_API sexp sexp_write_simple_object (sexp ctx, sexp self, sexp_sint_t n, sexp
 SEXP_API sexp sexp_finalize_port (sexp ctx, sexp self, sexp_sint_t n, sexp port);
 SEXP_API sexp sexp_make_input_port (sexp ctx, FILE* in, sexp name);
 SEXP_API sexp sexp_make_output_port (sexp ctx, FILE* out, sexp name);
+SEXP_API sexp sexp_make_non_null_input_port (sexp ctx, FILE* in, sexp name);
+SEXP_API sexp sexp_make_non_null_output_port (sexp ctx, FILE* out, sexp name);
 SEXP_API sexp sexp_port_binaryp_op (sexp ctx, sexp self, sexp_sint_t n, sexp port);
 SEXP_API sexp sexp_port_openp_op (sexp ctx, sexp self, sexp_sint_t n, sexp port);
 #if SEXP_USE_FOLD_CASE_SYMS
diff --git a/sexp.c b/sexp.c
index 06e5c3ef..cf4ad914 100644
--- a/sexp.c
+++ b/sexp.c
@@ -1407,6 +1407,16 @@ sexp sexp_make_output_port (sexp ctx, FILE* out, sexp name) {
   return p;
 }
 
+sexp sexp_make_non_null_input_port (sexp ctx, FILE* in, sexp name) {
+  if (!in) return sexp_user_exception(ctx, SEXP_FALSE, "null input-port", name);
+  return sexp_make_input_port(ctx, in, name);
+}
+
+sexp sexp_make_non_null_output_port (sexp ctx, FILE* out, sexp name) {
+  if (!out) return sexp_user_exception(ctx, SEXP_FALSE, "null output-port", name);
+  return sexp_make_output_port(ctx, out, name);
+}
+
 sexp sexp_port_binaryp_op (sexp ctx, sexp self, sexp_sint_t n, sexp port) {
   sexp_assert_type(ctx, sexp_portp, SEXP_IPORT, port);
   return sexp_make_boolean(sexp_port_binaryp(port));
diff --git a/tools/chibi-ffi b/tools/chibi-ffi
index 6c873660..39a60541 100755
--- a/tools/chibi-ffi
+++ b/tools/chibi-ffi
@@ -393,9 +393,9 @@
      ((string-type? base)
       (cat "sexp_c_string(ctx, " val ", -1)"))
      ((eq? 'input-port base)
-      (cat "sexp_make_input_port(ctx, " val ", SEXP_FALSE)"))
+      (cat "sexp_make_non_null_input_port(ctx, " val ", SEXP_FALSE)"))
      ((eq? 'output-port base)
-      (cat "sexp_make_output_port(ctx, " val ", SEXP_FALSE)"))
+      (cat "sexp_make_non_null_output_port(ctx, " val ", SEXP_FALSE)"))
      (else
       (let ((ctype (assq base *types*))
             (void*? (void-pointer-type? type)))