--- a/configure.ac	Wed May 31 12:51:24 2017 +0200
+++ b/configure.ac	Thu Jun 01 17:29:12 2017 +0200
@@ -45,6 +45,9 @@
 # Checks for header files.
 AC_CHECK_HEADERS([stdlib.h string.h dirent.h regex.h])
 
+# Check for regex function.
+AC_SEARCH_LIBS(regexec, regex)
+
 # Checks for typedefs, structures, and compiler characteristics.
 AC_CHECK_HEADER_STDBOOL
 AC_TYPE_SIZE_T