diff --git a/configure b/configure
index b63330cbff..5e3d6fbe47 100755
--- a/configure
+++ b/configure
@@ -2458,11 +2458,13 @@ case $target_os in
         objformat="win32"
         enable dos_paths
         check_cflags -fno-common
+        add_cppflags -U__STRICT_ANSI__
         ;;
     *-dos|freedos|opendos)
         network_extralibs="-lsocket"
         objformat="coff"
         enable dos_paths
+        add_cppflags -U__STRICT_ANSI__
         ;;
     linux)
         add_cppflags -D_POSIX_C_SOURCE=200112 -D_XOPEN_SOURCE=600