diff --git a/src/octTree.cpp b/src/octTree.cpp
index 91648cf..5435b25 100644
--- a/src/octTree.cpp
+++ b/src/octTree.cpp
@@ -32,6 +32,17 @@ OctTree::OctTree(const FCoordinates *particles, octPtr numParticles,
 	}
     }
   
+  lenNorm = 0;
+  for (octPtr i = 0; i < numParticles; i++)
+    {
+      for (int j = 0; j < 3; j++)
+	{
+	  float delta = particles[i][j]-xMin[j];
+	  if (delta > lenNorm)
+	    lenNorm = delta;
+	}
+    }
+  cout << xMin[0] << " " << xMin[1] << " " << xMin[2] << " lNorm=" << lenNorm << endl; 
 
   cells = new OctCell[numCells];
   Lbox = (float)(octCoordTypeNorm+1);
@@ -94,11 +105,14 @@ void OctTree::insertParticle(octPtr node,
     }
   
   for (int j = 0; j < 3; j++)
-    if ((octPtr)(particles[particleId][j]*Lbox) > icoord[j])
-      {
-	octPos |= (1 << j);
-	ipos[j] = 1;
-      }
+    {
+      float treePos = (particles[particleId][j]-xMin[j])*Lbox/lenNorm;
+      if ((octPtr)(treePos) > icoord[j])
+	{
+	  octPos |= (1 << j);
+	  ipos[j] = 1;
+	}
+    }
   
   if (cells[node].children[octPos] == emptyOctCell)
     {
diff --git a/src/octTree.hpp b/src/octTree.hpp
index 2402a5e..6dd846d 100644
--- a/src/octTree.hpp
+++ b/src/octTree.hpp
@@ -77,10 +77,10 @@ namespace CosmoTool
       for (int j = 0; j < 3; j++)
 	{
 	  center[j] = icoord[j]/(2.*octCoordCenter);
-	  realCenter[j] = center[j]*lenNorm+xMin[j];
+	  realCenter[j] = xMin[j] + center[j]*lenNorm;
 	}
       
-      f(realCenter, cells[node].numberLeaves, halfNodeLength/(float)octCoordCenter,
+      f(realCenter, cells[node].numberLeaves, lenNorm*halfNodeLength/(float)octCoordCenter,
 	cells[node].children[0] == invalidOctCell, // True if this is a meta-node
 	false);
       
@@ -104,7 +104,7 @@ namespace CosmoTool
 		}
 
 	      f(realCenter, 
-		1, halfNodeLength/(2.*octCoordCenter),
+		1, lenNorm*halfNodeLength/(2.*octCoordCenter),
 		false, true);
 	      continue;
 	    }