Index: include/base/periodic_boundaries.h
===================================================================
--- include/base/periodic_boundaries.h	(revision 4178)
+++ include/base/periodic_boundaries.h	(working copy)
@@ -53,8 +53,8 @@
 	       pairedboundary;
 
   PeriodicBoundary() :
-    myboundary(-1),
-    pairedboundary(-1),
+    myboundary(static_cast<unsigned int>(-1)),
+    pairedboundary(static_cast<unsigned int>(-1)),
     translation_vector()
   {
   }
@@ -75,8 +75,8 @@
   }
 
   PeriodicBoundary(const RealVectorValue & vector) :
-    myboundary(-1),
-    pairedboundary(-1),
+    myboundary(static_cast<unsigned int>(-1)),
+    pairedboundary(static_cast<unsigned int>(-1)),
     translation_vector (vector)
   {
   }