diff --git a/future/_mocks.php b/future/_mocks.php
index 7a18997c2e..dc0d13c599 100644
--- a/future/_mocks.php
+++ b/future/_mocks.php
@@ -806,6 +806,23 @@ public static function reset() {
 add_action( 'gravityview/template/after', function( $gravityview = null ) {
 	if ( defined( 'GRAVITYVIEW_FUTURE_CORE_ALPHA_ENABLED' ) && class_exists( '\GravityView_frontend' ) ) {
 		global $wp_filter;
+
+		if ( empty( $wp_filter['gravityview_after'] ) ) {
+			return;
+		}
+
+		/** WordPress 4.6 and lower compatibility, when WP_Hook classes were still absent. */
+		if ( is_array( $wp_filter['gravityview_after'] ) ) {
+			if ( ! empty( $wp_filter['gravityview_after'][10] ) ) {
+				foreach ( $wp_filter['gravityview_after'][10] as $function_key => $callback ) {
+					if ( strpos( $function_key, 'context_not_configured_warning' ) ) {
+						unset( $wp_filter['gravityview_after'][10][ $function_key ] );
+					}
+				}
+			}
+			return;
+		}
+
 		foreach ( $wp_filter['gravityview_after']->callbacks[10] as $function_key => $callback ) {
 			if ( strpos( $function_key, 'context_not_configured_warning' ) ) {
 				unset( $wp_filter['gravityview_after']->callbacks[10][ $function_key ] );