diff --git a/app/src/main/java/eu/faircode/email/Bimi.java b/app/src/main/java/eu/faircode/email/Bimi.java
index a7590cc46a..d80ebf26b2 100644
--- a/app/src/main/java/eu/faircode/email/Bimi.java
+++ b/app/src/main/java/eu/faircode/email/Bimi.java
@@ -222,9 +222,11 @@ public class Bimi {
 
                         // Check subject
                         boolean found = false;
+                        String root = UriHelper.getRootDomain(context, domain);
                         List<String> names = EntityCertificate.getDnsNames(cert);
                         for (String name : names)
-                            if (domain.endsWith(name.toLowerCase(Locale.ROOT))) {
+                            if (root != null &&
+                                    root.equalsIgnoreCase(UriHelper.getRootDomain(context, name))) {
                                 found = true;
                                 break;
                             }