diff --git a/src/core/logging.c b/src/core/logging.c
index 0d215f4..6941f9b 100644
--- a/src/core/logging.c
+++ b/src/core/logging.c
@@ -488,7 +488,7 @@
 {
 	int ret;
 	const char *c_subsys = NULL;
-	struct osmo_strbuf sb = { .buf = buf, .len = buf_len };
+	struct osmo_strbuf sb = { .buf = buf, .pos = buf, .len = buf_len };
 
 	/* safety net in case of encountering errors and returning nothing */
 	buf[0] = '\0';