diff --git a/grid/common/test/pantypeindexsettest.cc b/grid/common/test/pantypeindexsettest.cc
index a58202b6fd2e221e29ba8dae81fd5725bd98eee5..c556b161f5d63751885bc48a71c49aa99826f932 100644
--- a/grid/common/test/pantypeindexsettest.cc
+++ b/grid/common/test/pantypeindexsettest.cc
@@ -30,7 +30,7 @@ void checkPanTypeIndexSet(const PanTypeIndexSet<GridType,HostIndexSet>& panTypeI
     assert(panTypeIndexSet.geomTypes(codim) == hostIndexSet.geomTypes(codim));
     assert(panTypeIndexSet.size(codim) == hostIndexSet.size(codim));
 
-    for (int i=0; i<panTypeIndexSet.geomTypes(codim).size(); i++) {
+    for (size_t i=0; i<panTypeIndexSet.geomTypes(codim).size(); i++) {
       NewGeometryType type = panTypeIndexSet.geomTypes(codim)[i];
       assert(panTypeIndexSet.size(codim,type) == hostIndexSet.size(codim,type));
     }