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 4ff804e2c..f5d5a176f 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
@@ -157,6 +157,17 @@ public ListBoxModel doFillApiUriItems() {
             return getPossibleApiUriItems();
         }
 
+        public FormValidation doCheckAppID(@QueryParameter String appID) {
+            if (!appID.isEmpty()) {
+                try {
+                    Integer.parseInt(appID);
+                } catch (NumberFormatException x) {
+                    return FormValidation.warning("An app ID is likely to be a number, distinct from the app name");
+                }
+            }
+            return FormValidation.ok();
+        }
+
         @POST
         @SuppressWarnings("unused") // stapler
         @Restricted(NoExternalUse.class) // stapler