diff --git a/core/parser.c b/core/parser.c
index 6d62d4e..4e18e95 100644
--- a/core/parser.c
+++ b/core/parser.c
@@ -225,6 +225,14 @@ parse_ifdef(struct rifle_state *state, struct token *tok)
     return 0;
 }
 
+/*
+ * Handle an '#ifndef' directive
+ *
+ * @state: Compiler state
+ * @tok:   Last token
+ *
+ * Returns zero on success
+ */
 static int
 parse_ifndef(struct rifle_state *state, struct token *tok)
 {