diff --git a/wp-admin/network/settings.php b/wp-admin/network/settings.php
index 6349e8cdd0..1736511181 100644
--- a/wp-admin/network/settings.php
+++ b/wp-admin/network/settings.php
@@ -264,7 +264,7 @@ if ( isset( $_GET['updated'] ) ) {
 
 			<tr>
 				<th scope="row"><label for="upload_filetypes"><?php _e( 'Upload file types' ) ?></label></th>
-				<td><input name="upload_filetypes" type="text" id="upload_filetypes" class="large-text" value="<?php echo esc_attr( get_site_option('upload_filetypes', 'jpg jpeg png gif') ) ?>" size="45" /></td>
+				<td><input name="upload_filetypes" type="text" id="upload_filetypes" class="large-text" value="<?php echo esc_attr( get_site_option( 'upload_filetypes', 'jpg jpeg png gif' ) ) ?>" size="45" /></td>
 			</tr>
 
 			<tr>
diff --git a/wp-includes/ms-functions.php b/wp-includes/ms-functions.php
index 6d7a2fbd52..3fc6646834 100644
--- a/wp-includes/ms-functions.php
+++ b/wp-includes/ms-functions.php
@@ -1745,7 +1745,8 @@ function recurse_dirsize( $directory ) {
  * @return array
  */
 function check_upload_mimes( $mimes ) {
-	$site_exts = explode( ' ', get_site_option( 'upload_filetypes' ) );
+	$site_exts = explode( ' ', get_site_option( 'upload_filetypes', 'jpg jpeg png gif' ) );
+	$site_mimes = array();
 	foreach ( $site_exts as $ext ) {
 		foreach ( $mimes as $ext_pattern => $mime ) {
 			if ( $ext != '' && strpos( $ext_pattern, $ext ) !== false )