diff --git a/lib/log.js b/lib/log.js
index 37baab1..e08cab4 100644
--- a/lib/log.js
+++ b/lib/log.js
@@ -47,7 +47,7 @@ function toSource(thing, indent, visited) {
       result = '"' + thing + '"'
       break
     case 'number':
-      result = thing
+      result = '' + thing
       break
     case 'object':
       if (null === thing) {