diff --git a/src/client/conversation-viewer/conversation-web-view.vala b/src/client/conversation-viewer/conversation-web-view.vala
index 48b92317d8c143abc9452639e8c16e3572ee8c35..e46158f04d931c13cb6547323713cf55b9e03a0d 100644
--- a/src/client/conversation-viewer/conversation-web-view.vala
+++ b/src/client/conversation-viewer/conversation-web-view.vala
@@ -206,7 +206,8 @@ public class ConversationWebView : ClientWebView {
 
     private void on_deceptive_link_clicked(WebKit.JavascriptResult result) {
         try {
-            unowned JS.GlobalContext context = result.get_global_context();
+            unowned JS.GlobalContext context =
+                (JS.GlobalContext) result.get_global_context();
             JS.Object details = WebKitUtil.to_object(result);
 
             uint reason = (uint) Geary.JS.to_number(
diff --git a/src/client/util/util-webkit.vala b/src/client/util/util-webkit.vala
index 45a27c44d871363db2ee22d8cc25ba90f4f712b6..4957d1eea15dd5725f4412c3ecf45c000aeb6b36 100644
--- a/src/client/util/util-webkit.vala
+++ b/src/client/util/util-webkit.vala
@@ -18,7 +18,8 @@ namespace WebKitUtil {
      */
     public bool to_bool(WebKit.JavascriptResult result)
         throws Geary.JS.Error {
-        unowned JS.GlobalContext context = result.get_global_context();
+        unowned JS.GlobalContext context =
+            (JS.GlobalContext) result.get_global_context();
         unowned JS.Value value = result.get_value();
         if (!value.is_boolean(context)) {
             throw new Geary.JS.Error.TYPE("Result is not a JS Boolean object");
@@ -34,7 +35,7 @@ namespace WebKitUtil {
      */
     public inline double to_number(WebKit.JavascriptResult result)
         throws Geary.JS.Error {
-        return Geary.JS.to_number(result.get_global_context(),
+        return Geary.JS.to_number((JS.GlobalContext) result.get_global_context(),
                                   result.get_value());
     }
 
@@ -46,7 +47,7 @@ namespace WebKitUtil {
      */
     public inline string to_string(WebKit.JavascriptResult result)
         throws Geary.JS.Error {
-        return Geary.JS.to_string(result.get_global_context(),
+        return Geary.JS.to_string((JS.GlobalContext) result.get_global_context(),
                                   result.get_value());
     }
 
@@ -59,7 +60,8 @@ namespace WebKitUtil {
      */
     public string as_string(WebKit.JavascriptResult result)
         throws Geary.JS.Error {
-        unowned JS.GlobalContext context = result.get_global_context();
+        unowned JS.GlobalContext context =
+            (JS.GlobalContext) result.get_global_context();
         unowned JS.Value js_str_value = result.get_value();
         JS.Value? err = null;
         JS.String js_str = js_str_value.to_string_copy(context, out err);
@@ -78,7 +80,7 @@ namespace WebKitUtil {
      */
     public JS.Object? to_object(WebKit.JavascriptResult result)
         throws Geary.JS.Error {
-        return Geary.JS.to_object(result.get_global_context(),
+        return Geary.JS.to_object((JS.GlobalContext) result.get_global_context(),
                                   result.get_value());
     }