diff -r 153d0cafc1fd -r fc91c4a3dfe2 src/SemanticAnalysis.cpp
--- a/src/SemanticAnalysis.cpp	Sat Aug 04 23:26:49 2012 -0700
+++ b/src/SemanticAnalysis.cpp	Sat Aug 04 23:58:23 2012 -0700
@@ -1267,6 +1267,7 @@
     if (!desctable)
         return;
 
+    Vector<unsigned> composedList;
     StructureBufferBuilder builder;
 
     Local<Type> type(zone_);
@@ -1289,9 +1290,24 @@
             return;
 
         desctable->set(zone_, i, desc);
+
+        if (type->isStruct() || type->isArray()) {
+            if (!composedList.append(i))
+                return;
+        }
     }
 
-    Local<StructMap> map(zone_, StructMap::New(zone_, builder));
+    Local<FixedArray> composed(zone_);
+    if (composedList.length()) {
+        composed = FixedArray::New(zone_, composedList.length(), Heap::Tenure_Old);
+        if (!composed)
+            return;
+
+        for (unsigned i = 0; i < composedList.length(); i++)
+            composed->set(zone_, i, desctable->at(i));
+    }
+
+    Local<StructMap> map(zone_, StructMap::New(zone_, builder, composed));
     if (!map)
         return;