#error NO UPDATE-ALGORITHM DEFINED!
 #endif
 
-#include "obs_phi2.hpp"
-#include "obs_phi2_hist.hpp"
-
 o815 *O815;
 sim *Sim;
 
 const complex<double> _i_ = complex<double>(0.0,1.0);
 
+#include "obs_phi2.hpp"
+#include "obs_phi2_hist.hpp"
+#include "obs_phip2_hist.hpp"
+
 o815::comoption specOps[] = {
   { "mass", required_argument, NULL, 'm', "set mass", "min:max:inc" },
   { "", 0, NULL, 0, "", "" }
       *O815->out->log << "MASTER: registered observable: phi2_hist" << endl << flush;
       O815->observables.push_back(new obs_phi2_hist(O815));
     }
+    else if ( strcmp(*lonit, "phip2_hist") == 0 ) {
+      *O815->out->log << "MASTER: registered observable: phi2p_hist" << endl << flush;
+      O815->observables.push_back(new obs_phip2_hist(O815));
+    }
   }
 }