diff --git src/wp-includes/functions.php src/wp-includes/functions.php
index 28725e75473..2ee2be8a907 100644
--- src/wp-includes/functions.php
+++ src/wp-includes/functions.php
@@ -2365,7 +2365,7 @@ function wp_get_image_mime( $file ) {
 	 * we assume the file could not be validated.
 	 */
 	try {
-		if ( ! is_callable( 'exif_imagetype' ) ) {
+		if ( is_callable( 'exif_imagetype' ) ) {
 			$mime = image_type_to_mime_type( exif_imagetype( $file ) );
 		} elseif ( function_exists( 'getimagesize' ) ) {
 			$imagesize = getimagesize( $file );