diff -Naur wmweather+-2.18.orig/configure.ac wmweather+-2.18/configure.ac
--- wmweather+-2.18.orig/configure.ac	2020-04-24 20:31:43.000000000 +0200
+++ wmweather+-2.18/configure.ac	2021-01-03 00:25:30.443705781 +0100
@@ -18,6 +18,7 @@
 AC_SUBST(WMGENERAL_GUI)
 
 # Checks for programs.
+AM_PROG_AR
 AC_PROG_AWK
 AC_PROG_CC
 AC_PROG_CC_STDC