diff --git a/ssh.h b/ssh.h
index fb86f4f0..690d55c7 100644
--- a/ssh.h
+++ b/ssh.h
@@ -1732,6 +1732,7 @@ unsigned alloc_channel_id_general(tree234 *channels, size_t localid_offset);
               alloc_channel_id_general(tree, offsetof(type, localid)))
 
 void add_to_commasep(strbuf *buf, const char *data);
+void add_to_commasep_pl(strbuf *buf, ptrlen data);
 bool get_commasep_word(ptrlen *list, ptrlen *word);
 
 SeatPromptResult verify_ssh_host_key(
diff --git a/ssh/common.c b/ssh/common.c
index 0c9f51e3..424c8f71 100644
--- a/ssh/common.c
+++ b/ssh/common.c
@@ -607,11 +607,16 @@ unsigned alloc_channel_id_general(tree234 *channels, size_t localid_offset)
  * lists of protocol identifiers in SSH-2.
  */
 
-void add_to_commasep(strbuf *buf, const char *data)
+void add_to_commasep_pl(strbuf *buf, ptrlen data)
 {
     if (buf->len > 0)
         put_byte(buf, ',');
-    put_data(buf, data, strlen(data));
+    put_datapl(buf, data);
+}
+
+void add_to_commasep(strbuf *buf, const char *data)
+{
+    add_to_commasep_pl(buf, ptrlen_from_asciz(data));
 }
 
 bool get_commasep_word(ptrlen *list, ptrlen *word)