diff --git a/IntervalTree.h b/IntervalTree.h
index a6979a0..f309ecb 100644
--- a/IntervalTree.h
+++ b/IntervalTree.h
@@ -5,8 +5,7 @@
 #include <algorithm>
 #include <iostream>
 
-
-template <class T, typename K = int>
+template <class T, typename K = std::size_t>
 class Interval {
 public:
     K start;
@@ -20,12 +19,12 @@ class Interval {
 };
 
 template <class T, typename K>
-int intervalStart(const Interval<T,K>& i) {
+K intervalStart(const Interval<T,K>& i) {
     return i.start;
 }
 
 template <class T, typename K>
-int intervalStop(const Interval<T,K>& i) {
+K intervalStop(const Interval<T,K>& i) {
     return i.stop;
 }
 
@@ -35,7 +34,7 @@ template <class T, typename K>
     return out;
 }
 
-template <class T, typename K = int>
+template <class T, typename K = std::size_t>
 class IntervalStartSorter {
 public:
     bool operator() (const Interval<T,K>& a, const Interval<T,K>& b) {
@@ -43,7 +42,7 @@ class IntervalStartSorter {
     }
 };
 
-template <class T, typename K = int>
+template <class T, typename K = std::size_t>
 class IntervalTree {
 
 public:
@@ -54,7 +53,7 @@ class IntervalTree {
     intervalVector intervals;
     intervalTree* left;
     intervalTree* right;
-    int center;
+    K center;
 
     IntervalTree<T,K>(void)
         : left(NULL)
@@ -96,11 +95,11 @@ class IntervalTree {
 
     IntervalTree<T,K>(
             intervalVector& ivals,
-            unsigned int depth = 16,
-            unsigned int minbucket = 64,
-            int leftextent = 0,
-            int rightextent = 0,
-            unsigned int maxbucket = 512
+            std::size_t depth = 16,
+            std::size_t minbucket = 64,
+            K leftextent = 0,
+            K rightextent = 0,
+            std::size_t maxbucket = 512
             )
         : left(NULL)
         , right(NULL)
@@ -117,9 +116,9 @@ class IntervalTree {
               std::sort(ivals.begin(), ivals.end(), intervalStartSorter);
             }
 
-            int leftp = 0;
-            int rightp = 0;
-            int centerp = 0;
+            K leftp = 0;
+            K rightp = 0;
+            K centerp = 0;
             
             if (leftextent || rightextent) {
                 leftp = leftextent;