diff --git a/src/prim.c b/src/prim.c
index c2e7198..3f41c41 100644
--- a/src/prim.c
+++ b/src/prim.c
@@ -1,6 +1,8 @@
 #include <osmocom/core/utils.h>
 #include <osmocom/core/prim.h>
 
+/*! \brief human-readable string mapping for
+ *  \ref osmo_prim_operation */
 const struct value_string osmo_prim_op_names[5] = {
 	{ PRIM_OP_REQUEST,			"request" },
 	{ PRIM_OP_RESPONSE,			"response" },