diff --git a/wp-admin/includes/image.php b/wp-admin/includes/image.php
index 4ae53b9c3a..40cab01940 100644
--- a/wp-admin/includes/image.php
+++ b/wp-admin/includes/image.php
@@ -251,7 +251,15 @@ function wp_generate_attachment_metadata( $attachment_id, $file ) {
 			$editor = wp_get_image_editor( $file );
 
 			if ( ! is_wp_error( $editor ) ) { // No support for this type of file
-				$uploaded = $editor->save( $file, 'image/jpeg' );
+				/*
+				 * PDFs may have the same file filename as JPEGs.
+				 * Ensure the PDF preview image does not overwrite any JPEG images that already exist.
+				 */
+				$dirname = dirname( $file ) . '/';
+				$ext = '.' . pathinfo( $file, PATHINFO_EXTENSION );
+				$preview_file = $dirname . wp_unique_filename( $dirname, wp_basename( $file, $ext ) . '-pdf.jpg' );
+
+				$uploaded = $editor->save( $preview_file, 'image/jpeg' );
 				unset( $editor );
 
 				// Resize based on the full size image, rather than the source.
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 8a9f2ca079..76f0f66ec9 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-40132';
+$wp_version = '4.7.3-alpha-40133';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.