diff --git a/include/osmocom/core/utils.h b/include/osmocom/core/utils.h
index 9a6e6b2..92bea59 100644
--- a/include/osmocom/core/utils.h
+++ b/include/osmocom/core/utils.h
@@ -306,7 +306,7 @@
 		return 0;
 	if (sb->pos == NULL || sb->pos <= sb->buf)
 		return 0;
-	return OSMO_MIN(sb->pos - sb->buf, sb->len - 1);
+	return OSMO_MIN((size_t)(sb->pos - sb->buf), sb->len - 1);
 }
 
 /*! Return number of actual characters contained in struct osmo_strbuf (without terminating nul). */