diff --git a/src/stream.js b/src/stream.js
index 3027fba..1333f81 100644
--- a/src/stream.js
+++ b/src/stream.js
@@ -10,7 +10,7 @@ export class Iterator {
   static from(value) {
     if (!value) { return }
     const types = Iterator.handledTypes
-    const ctr = value.constructor || value.constructor
+    const ctr = value.constructor || value.prototype.constructor
 
     if (types.has(ctr)) {
       const handler = types.get(ctr)