diff --git a/src/octTree.cpp b/src/octTree.cpp
index a56e281..4ef929d 100644
--- a/src/octTree.cpp
+++ b/src/octTree.cpp
@@ -9,12 +9,27 @@ using namespace CosmoTool;
 
 //#define VERBOSE
 
+static uint32_t mypow(uint32_t i, uint32_t p)
+{
+  if (p == 0)
+    return 1;
+  else if (p == 1)
+    return i;
+
+  uint32_t k = p/2;
+  uint32_t j = mypow(i, k);
+  if (2*k==p)
+    return j*j;
+  else
+    return j*j*i;  
+}
+
 OctTree::OctTree(const FCoordinates *particles, octPtr numParticles, 
 		 uint32_t maxMeanTreeDepth, uint32_t maxAbsoluteDepth,
 		 uint32_t threshold)
 {
   cout << "MeanTree=" << maxMeanTreeDepth << endl;
-  numCells = pow(8, maxMeanTreeDepth);
+  numCells = mypow(8, maxMeanTreeDepth);
   assert(numCells < invalidOctCell);
   //#ifdef VERBOSE
   cerr << "Allocating " << numCells << " octtree cells" << endl;