diff --git a/src/mtxcmm.c b/src/mtxcmm.c
index 8f72279..b8e1d09 100644
--- a/src/mtxcmm.c
+++ b/src/mtxcmm.c
@@ -3571,7 +3571,9 @@ only need do IMG formatting because A is contained but can't contain IMG.
 And since image nesting is resolved before this stage, we only need to
 format simple IMG units holding their usual three ->args.
 */
-static void mtx_cmm_render_link_unit (MtxCmm *, MtxCmmParserUnit *, gchar *());
+static void mtx_cmm_render_link_unit (MtxCmm *self,
+                                      MtxCmmParserUnit *unit,
+                                      MtxCmmAImgFormatter *formatter);
 static void
 mtx_cmm_parser_merge_down_unit_arg_inlines (MtxCmm *self)
 {