diff --git a/src/Toolkit/Toolkit/GeoViewController.cs b/src/Toolkit/Toolkit/GeoViewController.cs
index 351f450c0..324a8ff25 100644
--- a/src/Toolkit/Toolkit/GeoViewController.cs
+++ b/src/Toolkit/Toolkit/GeoViewController.cs
@@ -201,7 +201,7 @@ public virtual Task<IdentifyGraphicsOverlayResult> IdentifyGraphicsOverlayAsync(
         /// <summary>
         /// Identifies the <see cref="GeoViewController"/> attached property.
         /// </summary>
-        public static BindableProperty GeoViewControllerProperty =
+        public static readonly BindableProperty GeoViewControllerProperty =
             BindableProperty.CreateAttached(
                 "GeoViewController",
                 typeof(GeoViewController),