diff -Naur a/configure.ac b/configure.ac
--- a/configure.ac	2015-08-16 19:50:08.000000000 +0000
+++ b/configure.ac	2020-05-14 18:59:25.974922568 +0000
@@ -33,7 +33,7 @@
 dnl Checks for libraries.
 check_popt=""
 AC_CHECK_LIB([popt], [main], check_popt=true)
-if test "x$check_popt" == x ; then
+if test "x$check_popt" = x ; then
 	AC_MSG_WARN([ libpopt not found.])
 else
 	POPT_LIBS=-lpopt
@@ -47,7 +47,7 @@
 
 check_iconv=""
 AC_CHECK_HEADERS([iconv.h],check_iconv=true)
-if test "x$check_iconv" == x ; then
+if test "x$check_iconv" = x ; then
 	AC_MSG_ERROR([*** iconv.h not found.])
 fi