diff --git a/config.m4 b/config.m4
index f7d1873..ee878a1 100644
--- a/config.m4
+++ b/config.m4
@@ -42,3 +42,24 @@ if test "$PHP_GNUPG" != "no"; then
 
   PHP_NEW_EXTENSION(gnupg, [gnupg.c gnupg_keylistiterator.c], $ext_shared)
 fi
+
+AC_ARG_WITH([gpg], [AS_HELP_STRING([--with-gpg],
+        [path to gpg v1.x])], [], [with_gpg=no])
+
+AC_PATH_PROG(GNUPG_PATH, gpg)
+if test "$with_gpg" != "no"; then
+  if test "$with_gpg" != "yes"; then
+    if test -x "$with_gpg"; then
+      ac_cv_path_GNUPG_PATH=$with_gpg
+    else
+      if test -x "$ac_cv_path_GNUPG_PATH"; then
+        AC_MSG_RESULT($with_gpg invalid: using $ac_cv_path_GNUPG_PATH)
+      else
+        AC_MSG_RESULT($with_gpg invalid)
+      fi
+    fi
+  fi
+  if test -x "$ac_cv_path_GNUPG_PATH"; then
+    AC_DEFINE_UNQUOTED([GNUPG_PATH], ["$ac_cv_path_GNUPG_PATH"], [Path to gpg v1.x])
+  fi
+fi