diff --git a/wp-includes/functions.php b/wp-includes/functions.php
index 01045f038d..b96e2aba67 100644
--- a/wp-includes/functions.php
+++ b/wp-includes/functions.php
@@ -2074,7 +2074,7 @@ function wp_unique_filename( $dir, $filename, $unique_filename_callback = null )
 
 			// Check for both lower and upper case extension or image sub-sizes may be overwritten.
 			while ( file_exists($dir . "/$filename") || file_exists($dir . "/$filename2") ) {
-				$new_number = $number + 1;
+				$new_number = (int) $number + 1;
 				$filename = str_replace( array( "-$number$ext", "$number$ext" ), "-$new_number$ext", $filename );
 				$filename2 = str_replace( array( "-$number$ext2", "$number$ext2" ), "-$new_number$ext2", $filename2 );
 				$number = $new_number;
@@ -2094,11 +2094,13 @@ function wp_unique_filename( $dir, $filename, $unique_filename_callback = null )
 		}
 
 		while ( file_exists( $dir . "/$filename" ) ) {
+			$new_number = (int) $number + 1;
 			if ( '' == "$number$ext" ) {
-				$filename = "$filename-" . ++$number;
+				$filename = "$filename-" . $new_number;
 			} else {
-				$filename = str_replace( array( "-$number$ext", "$number$ext" ), "-" . ++$number . $ext, $filename );
+				$filename = str_replace( array( "-$number$ext", "$number$ext" ), "-" . $new_number . $ext, $filename );
 			}
+			$number = $new_number;
 		}
 	}
 
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 84098484b2..4443f6503b 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.7.3-alpha-40071';
+$wp_version = '4.7.3-alpha-40075';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.