diff --git a/src/db/db/dbNetlistCompare.cc b/src/db/db/dbNetlistCompare.cc
index 29092538d..4d33db900 100644
--- a/src/db/db/dbNetlistCompare.cc
+++ b/src/db/db/dbNetlistCompare.cc
@@ -2016,7 +2016,7 @@ NetlistComparer::compare_circuits (const db::Circuit *c1, const db::Circuit *c2,
 
     std::sort (k.begin (), k.end ());
 
-    std::multimap<std::vector<std::pair<size_t, size_t> >, std::pair<const db::Device *, size_t> >::const_iterator dm = device_map.find (k);
+    std::multimap<std::vector<std::pair<size_t, size_t> >, std::pair<const db::Device *, size_t> >::iterator dm = device_map.find (k);
 
     if (! mapped || dm == device_map.end () || dm->first != k) {