diff --git a/api/src/org/labkey/api/study/actions/ParticipantVisitResolverChooser.java b/api/src/org/labkey/api/study/actions/ParticipantVisitResolverChooser.java
index c9a6d34f1ef..d0b733ea6b6 100644
--- a/api/src/org/labkey/api/study/actions/ParticipantVisitResolverChooser.java
+++ b/api/src/org/labkey/api/study/actions/ParticipantVisitResolverChooser.java
@@ -168,7 +168,7 @@ public void renderInputHtml(RenderContext ctx, HtmlWriter out, Object value)
                                             return ret2;
                                         }
                                     ),
-                                    disabledInput ? InputBuilder.hidden().name(_typeInputName).value(finalSelected.getName()).appendTo(out) : null
+                                    disabledInput ? InputBuilder.hidden().name(_typeInputName).value(finalSelected.getName()).getHtmlString() : null
                                 )
                             ).appendTo(out);
                         }