diff --git a/api/src/org/labkey/api/util/DOM.java b/api/src/org/labkey/api/util/DOM.java
index 2886fe8d34d..1dd3a432a3f 100644
--- a/api/src/org/labkey/api/util/DOM.java
+++ b/api/src/org/labkey/api/util/DOM.java
@@ -980,7 +980,7 @@ else if (key instanceof String)
                     }
                     else
                     {
-                        throw new IllegalArgumentException(String.valueOf(key));
+                        throw new IllegalArgumentException("Bad attribute in '" + tagName + "' element: " + String.valueOf(key));
                     }
                 }
                 // TODO again horrible hack, make this go away
diff --git a/api/src/org/labkey/api/util/DisplayElementBuilder.java b/api/src/org/labkey/api/util/DisplayElementBuilder.java
index 03e8c228cc1..f8e0446641a 100644
--- a/api/src/org/labkey/api/util/DisplayElementBuilder.java
+++ b/api/src/org/labkey/api/util/DisplayElementBuilder.java
@@ -85,6 +85,8 @@ public BUILDER onClick(String onClick)
 
     public BUILDER attributes(Map<String, String> attributes)
     {
+        if (attributes != null && attributes.containsKey(null))
+            throw new NullPointerException("Unexpected key value in attributes");
         if (attributes != null && !attributes.isEmpty())
             this.attributes = new TreeMap<>(attributes);
         else