diff --git a/src/main/java/org/jenkinsci/plugins/github_branch_source/GitHubAppCredentials.java b/src/main/java/org/jenkinsci/plugins/github_branch_source/GitHubAppCredentials.java
index 7fadf8f92..d3136c528 100644
--- a/src/main/java/org/jenkinsci/plugins/github_branch_source/GitHubAppCredentials.java
+++ b/src/main/java/org/jenkinsci/plugins/github_branch_source/GitHubAppCredentials.java
@@ -27,6 +27,7 @@
 import java.time.Instant;
 import java.util.HashMap;
 import java.util.List;
+import java.util.Locale;
 import java.util.Map;
 import java.util.concurrent.TimeUnit;
 import java.util.logging.Level;
@@ -231,14 +232,21 @@ static AppInstallationToken generateAppInstallationToken(
       if (appInstallations.size() == 1) {
         appInstallation = appInstallations.get(0);
       } else {
+        final String ownerOrEmpty = owner != null ? owner : "";
         appInstallation =
             appInstallations.stream()
-                .filter(installation -> installation.getAccount().getLogin().equals(owner))
+                .filter(
+                    installation ->
+                        installation
+                            .getAccount()
+                            .getLogin()
+                            .toLowerCase(Locale.ROOT)
+                            .equals(ownerOrEmpty.toLowerCase(Locale.ROOT)))
                 .findAny()
                 .orElseThrow(
                     () ->
                         new IllegalArgumentException(
-                            String.format(ERROR_NO_OWNER_MATCHING, appId, owner)));
+                            String.format(ERROR_NO_OWNER_MATCHING, appId, ownerOrEmpty)));
       }
 
       GHAppInstallationToken appInstallationToken =
diff --git a/src/test/java/org/jenkinsci/plugins/github_branch_source/GithubAppCredentialsTest.java b/src/test/java/org/jenkinsci/plugins/github_branch_source/GithubAppCredentialsTest.java
index 748882c9e..d0b262f84 100644
--- a/src/test/java/org/jenkinsci/plugins/github_branch_source/GithubAppCredentialsTest.java
+++ b/src/test/java/org/jenkinsci/plugins/github_branch_source/GithubAppCredentialsTest.java
@@ -100,7 +100,7 @@ public static void setUpJenkins() throws Exception {
             "sample",
             "54321",
             Secret.fromString(PKCS8_PRIVATE_KEY));
-    appCredentials.setOwner("cloudbeers");
+    appCredentials.setOwner("cloudBeers");
     store.addCredentials(Domain.global(), appCredentials);
     appCredentialsNoOwner =
         new GitHubAppCredentials(
@@ -536,7 +536,7 @@ public void testPassword() throws Exception {
         // ok
         assertEquals(
             e.getMessage(),
-            "Found multiple installations for GitHub app ID 54321 but none match credential owner \"null\". "
+            "Found multiple installations for GitHub app ID 54321 but none match credential owner \"\". "
                 + "Set the right owner in the credential advanced options");
       }