Index: wp-admin/includes/class-wp-debug-data.php
===================================================================
--- wp-admin/includes/class-wp-debug-data.php	(revision 55892)
+++ wp-admin/includes/class-wp-debug-data.php	(working copy)
@@ -237,8 +237,12 @@
 		}
 
 		// Check WP_ENVIRONMENT_TYPE.
-		if ( defined( 'WP_ENVIRONMENT_TYPE' ) && WP_ENVIRONMENT_TYPE ) {
-			$wp_environment_type = WP_ENVIRONMENT_TYPE;
+		if ( defined( 'WP_ENVIRONMENT_TYPE' ) ) {
+			if( WP_ENVIRONMENT_TYPE ) {
+				$wp_environment_type = WP_ENVIRONMENT_TYPE;
+			} else {
+				$wp_environment_type = __( 'Defined as empty' );
+			}
 		} else {
 			$wp_environment_type = __( 'Undefined' );
 		}