diff --git a/configure b/configure
index dacc6fc4387..5ecb68f851f 100755
--- a/configure
+++ b/configure
@@ -4104,6 +4104,7 @@ rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
     ;;
   *-mingw32*|*-cygwin*)
     enable_win16=${enable_win16:-no}
+    CFLAGS="$CFLAGS -D_WIN32"
     ;;
   i[3456789]86*)
     enable_win16=${enable_win16:-yes}
diff --git a/configure.ac b/configure.ac
index f7cf4b9137c..07962005717 100644
--- a/configure.ac
+++ b/configure.ac
@@ -165,6 +165,7 @@ case $host in
     ;;
   *-mingw32*|*-cygwin*)
     enable_win16=${enable_win16:-no}
+    CFLAGS="$CFLAGS -D_WIN32"
     ;;
   i[[3456789]]86*)
     enable_win16=${enable_win16:-yes}