diff --git a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/pgp/OpenPgpSignatureResultBuilder.java b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/pgp/OpenPgpSignatureResultBuilder.java
index e74879e43..e327180c3 100644
--- a/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/pgp/OpenPgpSignatureResultBuilder.java
+++ b/OpenKeychain/src/main/java/org/sufficientlysecure/keychain/pgp/OpenPgpSignatureResultBuilder.java
@@ -154,7 +154,7 @@ public class OpenPgpSignatureResultBuilder {
     private static boolean userIdListContainsAddress(String senderAddress, ArrayList<String> confirmedUserIds) {
         for (String rawUserId : confirmedUserIds) {
             UserId userId = OpenPgpUtils.splitUserId(rawUserId);
-            if (senderAddress.equals(userId.email)) {
+            if (senderAddress.equalsIgnoreCase(userId.email)) {
                 return true;
             }
         }