diff --git a/lisp/ob-C.el b/lisp/ob-C.el
index c3e72c680..42c60c296 100644
--- a/lisp/ob-C.el
+++ b/lisp/ob-C.el
@@ -233,6 +233,9 @@ its header arguments."
 		;; includes
 		(mapconcat
 		 (lambda (inc)
+		   ;; :includes '(<foo> <bar>) gives us a list of
+		   ;; symbols; convert those to strings.
+		   (when (symbolp inc) (setq inc (symbol-name inc)))
 		   (if (string-prefix-p "<" inc)
 		       (format "#include %s" inc)
 		     (format "#include \"%s\"" inc)))