proper dependency

diff --git a/libasn1parser/Makefile.am b/libasn1parser/Makefile.am
index f90a246..a1455f4 100644
--- a/libasn1parser/Makefile.am
+++ b/libasn1parser/Makefile.am
@@ -22,7 +22,7 @@
 	asn1p_ref.c asn1p_ref.h		\
 	asn1p_list.h
 
-asn1p_expr.h: asn1p_expr_str.h
+asn1parser.h: asn1p_expr_str.h
 
 asn1p_expr_str.h: expr-h.pl asn1p_expr.h
 	./expr-h.pl asn1p_expr.h > $@