--- a/configure
+++ b/configure
@@ -7197,6 +7197,9 @@
                                      $CONFIG_EXTRA      \
                                      $ALL_COMPONENTS    \
 
+echo "#if defined(HAVE_UNISTD_H) && HAVE_UNISTD_H == 0" >> $TMPH
+echo "#undef HAVE_UNISTD_H" >> $TMPH
+echo "#endif" >> $TMPH
 echo "#endif /* FFMPEG_CONFIG_H */" >> $TMPH
 echo "endif # FFMPEG_CONFIG_MAK" >> ffbuild/config.mak