diff --git a/cmdgen.c b/cmdgen.c
index 5216e753..78ac274e 100644
--- a/cmdgen.c
+++ b/cmdgen.c
@@ -816,7 +816,7 @@ int main(int argc, char **argv)
                     const ssh_keyalg *alg = find_pubkey_alg(ssh2alg);
                     if (alg)
                         bits = ssh_key_public_bits(
-                            alg, make_ptrlen(ssh2blob->s, ssh2blob->len));
+                            alg, ptrlen_from_strbuf(ssh2blob));
                     else
                         bits = -1;
                 } else {
diff --git a/misc.c b/misc.c
index 18edfb80..f360eebb 100644
--- a/misc.c
+++ b/misc.c
@@ -1243,6 +1243,16 @@ ptrlen make_ptrlen(const void *ptr, size_t len)
     return pl;
 }
 
+ptrlen ptrlen_from_asciz(const char *str)
+{
+    return make_ptrlen(str, strlen(str));
+}
+
+ptrlen ptrlen_from_strbuf(strbuf *sb)
+{
+    return make_ptrlen(sb->u, sb->len);
+}
+
 int ptrlen_eq_string(ptrlen pl, const char *str)
 {
     size_t len = strlen(str);
diff --git a/misc.h b/misc.h
index 968c3d5d..fd63b335 100644
--- a/misc.h
+++ b/misc.h
@@ -97,6 +97,8 @@ struct tm ltime(void);
 int nullstrcmp(const char *a, const char *b);
 
 ptrlen make_ptrlen(const void *ptr, size_t len);
+ptrlen ptrlen_from_asciz(const char *str);
+ptrlen ptrlen_from_strbuf(strbuf *sb);
 int ptrlen_eq_string(ptrlen pl, const char *str);
 char *mkstr(ptrlen pl);
 int string_length_for_printf(size_t);
diff --git a/ssh2userauth.c b/ssh2userauth.c
index 10a2d171..1d526d02 100644
--- a/ssh2userauth.c
+++ b/ssh2userauth.c
@@ -867,8 +867,8 @@ static void ssh2_userauth_process_queue(PacketProtocolLayer *ppl)
                                  BinarySink_UPCAST(sigblob));
                     strbuf_free(sigdata);
                     ssh2_userauth_add_sigblob(
-                        s, s->pktout, make_ptrlen(pkblob->s, pkblob->len),
-                        make_ptrlen(sigblob->s, sigblob->len));
+                        s, s->pktout, ptrlen_from_strbuf(pkblob),
+                        ptrlen_from_strbuf(sigblob));
                     strbuf_free(pkblob);
                     strbuf_free(sigblob);
 
diff --git a/sshpubk.c b/sshpubk.c
index 510eb585..309e634d 100644
--- a/sshpubk.c
+++ b/sshpubk.c
@@ -584,7 +584,7 @@ const ssh_keyalg *find_pubkey_alg_len(ptrlen name)
 
 const ssh_keyalg *find_pubkey_alg(const char *name)
 {
-    return find_pubkey_alg_len(make_ptrlen(name, strlen(name)));
+    return find_pubkey_alg_len(ptrlen_from_asciz(name));
 }
 
 struct ssh2_userkey *ssh2_load_userkey(const Filename *filename,
@@ -798,8 +798,8 @@ struct ssh2_userkey *ssh2_load_userkey(const Filename *filename,
     ret = snew(struct ssh2_userkey);
     ret->comment = comment;
     ret->key = ssh_key_new_priv(
-        alg, make_ptrlen(public_blob->u, public_blob->len),
-        make_ptrlen(private_blob->u, private_blob->len));
+        alg, ptrlen_from_strbuf(public_blob),
+        ptrlen_from_strbuf(private_blob));
     if (!ret->key) {
 	sfree(ret);
 	ret = NULL;