--- a/configure.ac
+++ b/configure.ac
@@ -842,7 +842,7 @@ ACX_CHECK_FORMAT_ATTRIBUTE
 ACX_CHECK_UNUSED_ATTRIBUTE
 
 # check OSX deployment target, if needed
-if echo $build_os | grep darwin > /dev/null; then
+if echo $target_os | grep darwin > /dev/null; then
   sdk_p=`xcode-select -print-path`;
   sdk_v="$( /usr/bin/xcrun --show-sdk-version )";
   case $sdk_v in
