diff --git a/src/wp-includes/media.php b/src/wp-includes/media.php
index 1e6a4e5f58..7bfda66f1c 100644
--- a/src/wp-includes/media.php
+++ b/src/wp-includes/media.php
@@ -1205,7 +1205,7 @@ function wp_calculate_image_srcset( $size_array, $image_src, $image_meta, $attac
 	$sources = apply_filters( 'wp_calculate_image_srcset', $sources, $size_array, $image_src, $image_meta, $attachment_id );
 
 	// Only return a 'srcset' value if there is more than one source.
-	if ( ! $src_matched || count( $sources ) < 2 ) {
+	if ( ! $src_matched || ! is_array( $sources ) || count( $sources ) < 2 ) {
 		return false;
 	}