diff --git a/unix/configure.ac b/unix/configure.ac
index c0756fdd..108ec86c 100644
--- a/unix/configure.ac
+++ b/unix/configure.ac
@@ -14,6 +14,8 @@ AM_INIT_AUTOMAKE([-Wall -Werror foreign])
 
 AC_PROG_INSTALL
 AC_PROG_RANLIB
+AM_PROG_AR
+AM_PROG_CC_C_O
 
 # Mild abuse of the '--enable' option format to allow manual
 # specification of setuid or setgid setup in pterm.