diff --git a/pdf.js b/pdf.js
index a4de3d8b2..68a2597d3 100644
--- a/pdf.js
+++ b/pdf.js
@@ -1010,7 +1010,7 @@ function IsArray(v) {
 }
 
 function IsStream(v) {
-    return typeof v == "object" && "getChar" in v;
+    return typeof v == "object" && v != null && ("getChar" in v);
 }
 
 function IsRef(v) {