diff --git a/sample/testAlgo.cpp b/sample/testAlgo.cpp
index c7dba56..65614f5 100644
--- a/sample/testAlgo.cpp
+++ b/sample/testAlgo.cpp
@@ -12,6 +12,7 @@ int main(int argc, char **argv)
   cout << square(2.1f) << endl;
   cout << cube(2.1f) << endl;
   
+  cout << spower<-2>(2.1f) << endl;
   cout << spower<2>(2.1f) << endl;
   cout << spower<3>(2.1f) << endl;
   cout << spower<4>(2.1f) << endl;
diff --git a/src/algo.hpp b/src/algo.hpp
index 9b6e892..485db75 100644
--- a/src/algo.hpp
+++ b/src/algo.hpp
@@ -25,6 +25,10 @@ namespace  CosmoTool
     template<typename T>
     static T spower(T a)
     {
+      if (N<0)
+        {
+          return 1/SPowerBase<-N>::spower(a);
+        }
       if ((N%2)==0)
 	{
 	  T b = SPowerBase<N/2>::spower(a);