diff --git a/.gitattributes b/.gitattributes
index 4bb443c..e8270cc 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -1 +1,2 @@
-*.pdf binary
\ No newline at end of file
+*.pdf binary
+*.pdf diff
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7f0f211..bddec07 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
+### Fixed
+- Fixed `Name must start with a leading slash` when adding an external document to a `pdfjs` document, and adding that result to another `pdfjs` document again (caused by a `null` object reference due to object streams). Also fixes duplicate objects when adding external documents with
+pages in object streams.
 
 ## [2.5.2]
 ### Fixed
diff --git a/lib/external.js b/lib/external.js
index 34cb3b6..b1abfe3 100644
--- a/lib/external.js
+++ b/lib/external.js
@@ -48,6 +48,12 @@ module.exports = class ExternalDocument {
     const kids = this.pages.get("Kids");
     const filter = page ? (i) => i === page - 1 : undefined;
 
+    // As a first iteration, simply register all page objects to ensure they exist for inter-page
+    // references (as they are not part of the `addObjectsRecursive` in the second iteration)
+    for (const page of this._iterPagesRecursively(doc, kids, filter)) {
+      doc._registerObject(page, true);
+    }
+
     for (const page of this._iterPagesRecursively(doc, kids, filter)) {
       // if the page object does not define its MediaBox, explicitly set its MediaBox to the
       // value defined by its parent Pages object
@@ -55,9 +61,6 @@ module.exports = class ExternalDocument {
         page.properties.set("MediaBox", this.mediaBox);
       }
 
-      // add single page
-      doc._registerObject(page, true);
-
       // first, register objects to assign IDs (for references)
       const objects = [];
       Parser.addObjectsRecursive(objects, page, 0);
diff --git a/lib/object/reference.js b/lib/object/reference.js
index 76eef72..77618e0 100644
--- a/lib/object/reference.js
+++ b/lib/object/reference.js
@@ -21,6 +21,9 @@ class PDFReference {
   }
 
   toString() {
+    if (this.object.id === null) {
+      throw new TypeError("Tried to write reference with `null` object id");
+    }
     return this.object.id + " " + this.object.rev + " R";
   }
 
diff --git a/lib/parser/parser.js b/lib/parser/parser.js
index 55d6816..c6629b8 100644
--- a/lib/parser/parser.js
+++ b/lib/parser/parser.js
@@ -68,6 +68,13 @@ class Parser {
         if (objects.indexOf(value.object) > -1) {
           break;
         }
+
+        // skip references to other pages
+        const type = value.object.properties.get("Type");
+        if (type && type.toString() === "/Page") {
+          break;
+        }
+
         objects.push(value.object);
         Parser.addObjectsRecursive(objects, value.object);
         break;
diff --git a/test/pdfs/external/addallpages.pdf b/test/pdfs/external/addallpages.pdf
index d79eaa4..4ea8454 100644
Binary files a/test/pdfs/external/addallpages.pdf and b/test/pdfs/external/addallpages.pdf differ
diff --git a/test/pdfs/external/addinbetween.pdf b/test/pdfs/external/addinbetween.pdf
index af84d59..3feb893 100644
Binary files a/test/pdfs/external/addinbetween.pdf and b/test/pdfs/external/addinbetween.pdf differ
diff --git a/test/pdfs/external/self.pdf b/test/pdfs/external/self.pdf
index 1e1ae6b..d7ef3f8 100644
Binary files a/test/pdfs/external/self.pdf and b/test/pdfs/external/self.pdf differ
diff --git a/test/pdfs/issue/issue-112.pdf b/test/pdfs/issue/issue-112.pdf
index 6d97786..59600dd 100644
Binary files a/test/pdfs/issue/issue-112.pdf and b/test/pdfs/issue/issue-112.pdf differ
diff --git a/test/pdfs/issue/issue-117-nested-pages.pdf b/test/pdfs/issue/issue-117-nested-pages.pdf
index 58d422d..d4be53a 100644
Binary files a/test/pdfs/issue/issue-117-nested-pages.pdf and b/test/pdfs/issue/issue-117-nested-pages.pdf differ