diff --git a/src/sdk.js b/src/sdk.js
index 22deef75b..00c98a1f1 100644
--- a/src/sdk.js
+++ b/src/sdk.js
@@ -95,12 +95,17 @@ class OpenForm {
     CSPNonce.setValue(CSPNonceValue);
     initialiseSentry(sentryDSN, sentryEnv);
 
-    // ensure that the basename has no trailing slash (for react router)
-    let pathname = basePath || window.location.pathname;
-    if (pathname.endsWith('/')) {
-      pathname = pathname.slice(0, pathname.length - 1);
+    if (useHashRouting) {
+      this.basePath = '';
+    } else {
+      // ensure that the basename has no trailing slash (for react router)
+      let pathname = basePath || window.location.pathname;
+      if (pathname.endsWith('/')) {
+        pathname = pathname.slice(0, pathname.length - 1);
+      }
+      this.basePath = pathname;
     }
-    this.basePath = pathname;
+
     this.calculateClientBaseUrl();
   }
 
diff --git a/src/sdk.spec.js b/src/sdk.spec.js
index e9e4e7d15..ebc55b23d 100644
--- a/src/sdk.spec.js
+++ b/src/sdk.spec.js
@@ -136,6 +136,6 @@ describe('OpenForm', () => {
       useHashRouting: true,
     });
 
-    expect(form.clientBaseUrl).toEqual('http://localhost/some-server-side/path#/some-subpath');
+    expect(form.clientBaseUrl).toEqual('http://localhost/some-server-side/path#/');
   });
 });