diff --git a/src/THcShowerArray.cxx b/src/THcShowerArray.cxx
index eb212e1c195ee1a112c9f8652c13bc46d39c5cb2..dc246b2c1dbd7dc38a895097dd8fdbcb57845cbf 100644
--- a/src/THcShowerArray.cxx
+++ b/src/THcShowerArray.cxx
@@ -281,7 +281,7 @@ Int_t THcShowerArray::ReadDatabase( const TDatime& date )
     {0}
   };
 
-   for(UInt_t ip=0;ip<fNelem;ip++) {
+   for(Int_t ip=0;ip<fNelem;ip++) {
     fAdcTimeWindowMin[ip] = -1000.;
     fAdcTimeWindowMax[ip] = 1000.;
    }