diff --git a/configure.ac b/configure.ac
index 2e829b2..8874db6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -109,7 +109,7 @@ if test "$WITH_LIBGCRYPT" != no; then
   WITH_LIBGCRYPT=$ac_cv_lib_gcrypt_gcry_control
 fi
 # gnutls_base64_encode2() was added >8 years ago so should be present
-AM_CONDITIONAL(TEST_CHAP_BASE64, [test "$WITH_LIBGCRYPT"])
+AM_CONDITIONAL(TEST_CHAP_BASE64, [test "$WITH_GNUTLS" = yes])
 
 NEED_MD5=no
 if test "$WITH_GNUTLS" = no && test "$WITH_LIBGCRYPT" = no; then