diff --git a/configure.in b/configure.in
index 96e29fe719b..9fcf264126f 100644
--- a/configure.in
+++ b/configure.in
@@ -1881,6 +1881,14 @@ if test -f /usr/lpp/X11/bin/smt.exp; then
   AC_DEFINE(HAVE_AIX_SMT_EXP)
 fi
 
+AC_MSG_CHECKING(whether system supports dynamic ptys)
+if test -d /dev/pts && ls -d /dev/ptmx > /dev/null 2>&1 ; then
+  AC_MSG_RESULT(yes)
+  AC_DEFINE(HAVE_DEV_PTMX)
+else
+  AC_MSG_RESULT(no)
+fi
+
 # Set up the CFLAGS for real compilation, so we can substitute it.
 CFLAGS="$REAL_CFLAGS"