diff --git a/apiv2/impl-ecl.lisp b/apiv2/impl-ecl.lisp
index 3a32ff6..19db981 100644
--- a/apiv2/impl-ecl.lisp
+++ b/apiv2/impl-ecl.lisp
@@ -16,7 +16,8 @@
   mp:*current-process*)
 
 (defun %thread-name (thread)
-  (mp:process-name thread))
+  ;; Some system threads have symbols for a name.
+  (string (mp:process-name thread)))
 
 (defun %join-thread (thread)
   (mp:process-join thread))
diff --git a/test/tests-v2.lisp b/test/tests-v2.lisp
index 72d8588..9fbde96 100644
--- a/test/tests-v2.lisp
+++ b/test/tests-v2.lisp
@@ -44,6 +44,10 @@
   (is (equal "foo" (thread-name
                     (make-thread (lambda () t) :name "foo")))))
 
+(test thread-name.all-strings
+  (is (every #'(lambda (thread) (stringp (thread-name thread)))
+             (all-threads))))
+
 (defparameter *some-special* :global-value)
 
 (test default-special-bindings.sees-global-bindings