diff --git a/toolchain/android-toolchain-clang.xml b/toolchain/android-toolchain-clang.xml
index a6583b3b8..6ebbd5001 100644
--- a/toolchain/android-toolchain-clang.xml
+++ b/toolchain/android-toolchain-clang.xml
@@ -92,6 +92,9 @@
   <flag value ="-shared" />
   <flag value="--target=${ABITRIPLE}${PLATFORM_NUMBER}" />
 
+  <!-- Build time error, not run time -->
+  <flag value="-Wl,--no-undefined" unless="HXCPP_ALLOW_UNDEFINED" />
+
   <flag value ="-static-libstdc++" />
   <!-- This shows the android link line, which may be so long that it breaks the tool
      https://github.com/HaxeFoundation/hxcpp/pull/1091
diff --git a/tools/hxcpp/BuildTool.hx b/tools/hxcpp/BuildTool.hx
index 8e20a1469..d6b42f513 100644
--- a/tools/hxcpp/BuildTool.hx
+++ b/tools/hxcpp/BuildTool.hx
@@ -2216,6 +2216,13 @@ class BuildTool
       }
    }
 
+   function dumpDefs()
+   {
+      Sys.println("Defines:");
+      for(k in mDefines.keys())
+         Sys.println('  $k=${mDefines.get(k)}');
+   }
+
    function parseXML(inXML:XmlAccess,inSection:String, forceRelative:Bool)
    {
       for(el in inXML.elements)
@@ -2225,9 +2232,14 @@ class BuildTool
             switch(el.name)
             {
                case "set" :
-                  var name = substitute(el.att.name);
-                  var value = substitute(el.att.value);
-                  mDefines.set(name,value);
+                  if (el.has.name)
+                  {
+                     var name = substitute(el.att.name);
+                     var value = substitute(el.att.value);
+                     mDefines.set(name,value);
+                  }
+                  else
+                     dumpDefs();
                case "unset" :
                   var name = substitute(el.att.name);
                   mDefines.remove(name);