diff --git a/src/core/xref.js b/src/core/xref.js
index 3f7dd61a0..5473c335c 100644
--- a/src/core/xref.js
+++ b/src/core/xref.js
@@ -21,15 +21,7 @@ import {
   InvalidPDFException,
   warn,
 } from "../shared/util.js";
-import {
-  Cmd,
-  Dict,
-  isCmd,
-  isDict,
-  isRef,
-  isStream,
-  Ref,
-} from "./primitives.js";
+import { Cmd, Dict, isCmd, Ref } from "./primitives.js";
 import {
   DocStats,
   MissingDataException,
@@ -38,6 +30,7 @@ import {
   XRefParseException,
 } from "./core_utils.js";
 import { Lexer, Parser } from "./parser.js";
+import { BaseStream } from "./base_stream.js";
 import { CipherTransformFactory } from "./crypto.js";
 
 class XRef {
@@ -88,7 +81,7 @@ class XRef {
       }
       warn(`XRef.parse - Invalid "Encrypt" reference: "${ex}".`);
     }
-    if (isDict(encrypt)) {
+    if (encrypt instanceof Dict) {
       const ids = trailerDict.get("ID");
       const fileId = ids && ids.length ? ids[0] : "";
       // The 'Encrypt' dictionary itself should not be encrypted, and by
@@ -113,7 +106,7 @@ class XRef {
       }
       warn(`XRef.parse - Invalid "Root" reference: "${ex}".`);
     }
-    if (isDict(root) && root.has("Pages")) {
+    if (root instanceof Dict && root.has("Pages")) {
       this.root = root;
     } else {
       if (!recoveryMode) {
@@ -155,10 +148,10 @@ class XRef {
     let dict = parser.getObj();
 
     // The pdflib PDF generator can generate a nested trailer dictionary
-    if (!isDict(dict) && dict.dict) {
+    if (!(dict instanceof Dict) && dict.dict) {
       dict = dict.dict;
     }
-    if (!isDict(dict)) {
+    if (!(dict instanceof Dict)) {
       throw new FormatError(
         "Invalid XRef table: could not parse trailer dictionary"
       );
@@ -564,7 +557,7 @@ class XRef {
       }
       // read the trailer dictionary
       const dict = parser.getObj();
-      if (!isDict(dict)) {
+      if (!(dict instanceof Dict)) {
         continue;
       }
       // Do some basic validation of the trailer/root dictionary candidate.
@@ -656,7 +649,7 @@ class XRef {
           if (
             !Number.isInteger(parser.getObj()) ||
             !isCmd(parser.getObj(), "obj") ||
-            !isStream((obj = parser.getObj()))
+            !((obj = parser.getObj()) instanceof BaseStream)
           ) {
             throw new FormatError("Invalid XRef stream");
           }
@@ -675,7 +668,7 @@ class XRef {
         obj = dict.get("Prev");
         if (Number.isInteger(obj)) {
           this.startXRefQueue.push(obj);
-        } else if (isRef(obj)) {
+        } else if (obj instanceof Ref) {
           // The spec says Prev must not be a reference, i.e. "/Prev NNN"
           // This is a fallback for non-compliant PDFs, i.e. "/Prev NNN 0 R"
           this.startXRefQueue.push(obj.num);
@@ -746,9 +739,9 @@ class XRef {
     } else {
       xrefEntry = this.fetchCompressed(ref, xrefEntry, suppressEncryption);
     }
-    if (isDict(xrefEntry)) {
+    if (xrefEntry instanceof Dict) {
       xrefEntry.objId = ref.toString();
-    } else if (isStream(xrefEntry)) {
+    } else if (xrefEntry instanceof BaseStream) {
       xrefEntry.dict.objId = ref.toString();
     }
     return xrefEntry;
@@ -790,7 +783,7 @@ class XRef {
     } else {
       xrefEntry = parser.getObj();
     }
-    if (!isStream(xrefEntry)) {
+    if (!(xrefEntry instanceof BaseStream)) {
       if (
         typeof PDFJSDev === "undefined" ||
         PDFJSDev.test("!PRODUCTION || TESTING")
@@ -808,7 +801,7 @@ class XRef {
   fetchCompressed(ref, xrefEntry, suppressEncryption = false) {
     const tableOffset = xrefEntry.offset;
     const stream = this.fetch(Ref.get(tableOffset, 0));
-    if (!isStream(stream)) {
+    if (!(stream instanceof BaseStream)) {
       throw new FormatError("bad ObjStm stream");
     }
     const first = stream.dict.get("First");
@@ -859,7 +852,7 @@ class XRef {
 
       const obj = parser.getObj();
       entries[i] = obj;
-      if (isStream(obj)) {
+      if (obj instanceof BaseStream) {
         continue;
       }
       const num = nums[i],