diff --git a/compiler/image_writer.cc b/compiler/image_writer.cc
index be720ad..eaeacc5 100644
--- a/compiler/image_writer.cc
+++ b/compiler/image_writer.cc
@@ -437,6 +437,9 @@
       continue;
     }
     const DexFile* dex_file = dex_cache->GetDexFile();
+    CHECK(dex_file_oat_index_map_.find(dex_file) != dex_file_oat_index_map_.end())
+        << "Dex cache should have been pruned " << dex_file->GetLocation()
+        << "; possibly in class path";
     DexCacheArraysLayout layout(target_ptr_size_, dex_file);
     DCHECK(layout.Valid());
     size_t oat_index = GetOatIndexForDexCache(dex_cache);