diff --git a/src/wp-admin/includes/file.php b/src/wp-admin/includes/file.php
index 1fbfe39678..79e2d48103 100644
--- a/src/wp-admin/includes/file.php
+++ b/src/wp-admin/includes/file.php
@@ -1661,7 +1661,7 @@ function _unzip_file_ziparchive( $file, $to, $needed_dirs = array() ) {
 	 * Require we have enough space to unzip the file and copy its contents, with a 10% buffer.
 	 */
 	if ( wp_doing_cron() ) {
-		$available_space = @disk_free_space( WP_CONTENT_DIR );
+		$available_space = function_exists( 'disk_free_space' ) ? @disk_free_space( WP_CONTENT_DIR ) : false;
 
 		if ( $available_space && ( $uncompressed_size * 2.1 ) > $available_space ) {
 			return new WP_Error(
@@ -1802,7 +1802,7 @@ function _unzip_file_pclzip( $file, $to, $needed_dirs = array() ) {
 	 * Require we have enough space to unzip the file and copy its contents, with a 10% buffer.
 	 */
 	if ( wp_doing_cron() ) {
-		$available_space = @disk_free_space( WP_CONTENT_DIR );
+		$available_space = function_exists( 'disk_free_space' ) ? @disk_free_space( WP_CONTENT_DIR ) : false;
 
 		if ( $available_space && ( $uncompressed_size * 2.1 ) > $available_space ) {
 			return new WP_Error(
diff --git a/src/wp-admin/includes/update-core.php b/src/wp-admin/includes/update-core.php
index 63538751ae..c150adc26f 100644
--- a/src/wp-admin/includes/update-core.php
+++ b/src/wp-admin/includes/update-core.php
@@ -1242,7 +1242,7 @@ function update_core( $from, $to ) {
 
 		// If we don't have enough free space, it isn't worth trying again.
 		// Unlikely to be hit due to the check in unzip_file().
-		$available_space = @disk_free_space( ABSPATH );
+		$available_space = function_exists( 'disk_free_space' ) ? @disk_free_space( ABSPATH ) : false;
 
 		if ( $available_space && $total_size >= $available_space ) {
 			$result = new WP_Error( 'disk_full', __( 'There is not enough free disk space to complete the update.' ) );