diff --git a/trunk/auto/depends.sh b/trunk/auto/depends.sh
index 3b5c74c50..e3d9e5f94 100644
--- a/trunk/auto/depends.sh
+++ b/trunk/auto/depends.sh
@@ -361,6 +361,9 @@ if [ $SRS_EXPORT_LIBRTMP_PROJECT = NO ]; then
     OSX_prepare; ret=$?; if [[ 0 -ne $ret ]]; then echo "OSX prepare failed, ret=$ret"; exit $ret; fi
 fi
 
+# the sed command
+SED="sed -i" && if [ $OS_IS_OSX = YES ]; then SED="sed -i ''"; fi
+
 #####################################################################################
 # check the os.
 #####################################################################################
diff --git a/trunk/auto/setup_variables.sh b/trunk/auto/setup_variables.sh
index bb517aef1..d1d643b4f 100644
--- a/trunk/auto/setup_variables.sh
+++ b/trunk/auto/setup_variables.sh
@@ -28,7 +28,3 @@ if [[ -z $SrsArmCXX ]]; then SrsArmCXX=$__SrsArmCXX; fi
 if [[ -z $SrsArmAR ]]; then SrsArmAR=$__SrsArmAR; fi
 if [[ -z $SrsArmLD ]]; then SrsArmLD=$__SrsArmLD; fi
 if [[ -z $SrsArmRANDLIB ]]; then SrsArmRANDLIB=$__SrsArmRANDLIB; fi
-
-# the sed command
-SED="sed -i"
-if [ $OS_IS_OSX = YES ]; then SED="sed -i ''"; fi