diff --git a/cache/coherence.hpp b/cache/coherence.hpp
index b10777a..a5fa171 100644
--- a/cache/coherence.hpp
+++ b/cache/coherence.hpp
@@ -67,6 +67,8 @@ class InnerCohPortBase
       return std::make_pair(-1, policy);
     } else {
       coh.push_back(c);
+      assert(coh.size() <= 64 || 0 ==
+             "Only 64 coherent inner caches are supported for now as the directory in class MetadataDirectoryBase is implemented as a 64-bit  bitmap.");
       return std::make_pair(coh.size()-1, policy);
     }
   }