diff --git a/src/Makefile b/src/Makefile
index d1a477c6dfd80b8fbe0f362d777d230c12fed152..67a637f7670c7cff4bceec9dc36a2bbc4ffac1f1 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -2,7 +2,7 @@ CXX = g++
 MPICXX = mpic++
 LD = g++
 MPILD = mpic++
-CFLAGS = -Wall -g -O3  -Wno-unused-variable
+CFLAGS = -Wall -g -O3  -Wno-unused-variable -std=c++11
 LDOPT = -lginac
 
 MPIEXEC = mpiexec
@@ -23,7 +23,7 @@ tensormatrix_mpi: $(MPIOBJ)
 	$(MPICXX) $(CFLAGS) -o $@ -c $<
 
 run: tensormatrix_mpi
-	$(MPIEXEC) -n $(NP) $<
+	$(MPIEXEC) --oversubscribe -n $(NP) $<
 
 clean:
 	@rm -f *.o tensormatrix_mpi tensormatrix
diff --git a/src/utils_parall.cpp b/src/utils_parall.cpp
index 3dc25d10f5695ae158e8fe36840b013fb2e2cc2f..5fdb2af05594cf83ef27c7598e7f7e4a2e0f423b 100644
--- a/src/utils_parall.cpp
+++ b/src/utils_parall.cpp
@@ -1,4 +1,5 @@
 #include <iostream>
+#include <sstream>
 #include <mpi.h>
 
 #include "utils_parall.h"