diff --git a/src/highlight.c b/src/highlight.c
index fa32981..efbc5b1 100644
--- a/src/highlight.c
+++ b/src/highlight.c
@@ -343,6 +343,7 @@
     NULL
 };
 
+#if defined(FEAT_SYN_HL) || defined(PROTO)
 /*
  * Returns the number of highlight groups.
  */
@@ -369,6 +370,7 @@
 {
     return HL_TABLE()[id].sg_link;
 }
+#endif
 
     void
 init_highlight(