diff --git a/src/shared/utils/OneSignalUtils.ts b/src/shared/utils/OneSignalUtils.ts
index ad2316c17..8d20c6552 100644
--- a/src/shared/utils/OneSignalUtils.ts
+++ b/src/shared/utils/OneSignalUtils.ts
@@ -72,11 +72,26 @@ export class OneSignalUtils {
     }
 
     const windowEnv = SdkEnvironment.getWindowEnv();
-    return (
+
+    const isHttp = location.protocol === 'http:';
+    const useSubdomain =
       (windowEnv === WindowEnvironmentKind.Host ||
         windowEnv === WindowEnvironmentKind.CustomIframe) &&
-      (!!subdomain || location.protocol === 'http:')
-    );
+      (!!subdomain || isHttp);
+
+    if (useSubdomain) {
+      if (isHttp) {
+        throw new Error(
+          "OneSignalSDK: HTTP sites are no longer supported starting with version 16 (User Model), your public site must start with https://. Please visit the OneSignal dashboard's Settings > Web Configuration to find this option.",
+        );
+      } else {
+        throw new Error(
+          'OneSignalSDK: The "My site is not fully HTTPS" option is no longer supported starting with version 16 (User Model) of the OneSignal SDK. Please visit the OneSignal dashboard\'s Settings > Web Configuration to find this option.',
+        );
+      }
+    }
+
+    return false;
   }
 
   public static redetectBrowserUserAgent(): IBowser {