JavaScriptSolidServer
diff --git a/solid-oidc.js b/solid-oidc.js
@@ -421,6 +421,11 @@ export class Session extends EventTarget {
     this._idpDetails = null
     this._refreshPromise = null
 
+    // Bind so authFetch survives being passed by reference (drop-in fetch):
+    // consumers hand it to rdflib / solid-logic / rdf-dereference as a bare
+    // `fetch`, which would otherwise lose `this`.
+    this.authFetch = this.authFetch.bind(this)
+
     // Set up event listeners
     if (this.onStateChange) {
       this.addEventListener(SessionEvents.STATE_CHANGE, this.onStateChange)

diff --git a/test.html b/test.html
@@ -256,6 +256,23 @@ <h1>solid-oidc tests</h1>
       }
     })
 
+    asyncTest('Session: authFetch survives being passed by reference (bound)', async () => {
+      const session = new Session()
+      // Bare reference, the way rdflib / solid-logic / rdf-dereference take it.
+      // Before binding this throws "Cannot read properties of undefined (reading '_isActive')".
+      const { authFetch } = session
+      const origFetch = globalThis.fetch
+      globalThis.fetch = async () => new Response(null, { status: 200 })
+      try {
+        await authFetch('https://example.com', { method: 'HEAD' })
+        assert(true, 'authFetch is callable when passed by reference')
+      } catch (e) {
+        assert(false, `authFetch lost its binding when passed by reference: ${e.message}`)
+      } finally {
+        globalThis.fetch = origFetch
+      }
+    })
+
     // ==========================================================================
     // Summary
     // ==========================================================================