diff --git a/configure.in b/configure.in
index ece5f03a4c3da5baef4e3b2fd5da16c70e5eca28..527f9c8e0b4d536d300fb66f7676da52775f6c6b 100644
--- a/configure.in
+++ b/configure.in
@@ -456,6 +456,9 @@ FPTOOLS_CHECK_ALIGNMENT(double)
 dnl ** do we have long longs?
 FPTOOLS_C_LONG_LONG
 
+dnl ** can we open files in binary mode?
+FPTOOLS_O_BINARY
+
 #
 dnl ** check for specific library functions that we are interested in
 #