diff --git a/src/libutil/hash.cc b/src/libutil/hash.cc
index 6b45ac859..817ddc0b8 100644
--- a/src/libutil/hash.cc
+++ b/src/libutil/hash.cc
@@ -45,6 +45,8 @@ bool Hash::operator != (const Hash & h2) const
 
 bool Hash::operator < (const Hash & h) const
 {
+    if (hashSize < h.hashSize) return true;
+    if (hashSize > h.hashSize) return false;
     for (unsigned int i = 0; i < hashSize; i++) {
         if (hash[i] < h.hash[i]) return true;
         if (hash[i] > h.hash[i]) return false;