diff --git a/src/loadGadget.cpp b/src/loadGadget.cpp
index 171e7d8..4a3952e 100644
--- a/src/loadGadget.cpp
+++ b/src/loadGadget.cpp
@@ -337,7 +337,7 @@ SimuData *CosmoTool::loadGadgetMulti(const char *fname, int id,
         }
 
 	f->beginCheckpoint();
-	data->Id = new long[data->NumPart];
+	data->Id = new int64_t[data->NumPart];
 	if (data->Id == 0)
 	  {
 	    delete f;
diff --git a/src/loadSimu.hpp b/src/loadSimu.hpp
index 2eb5ac8..bb1ddba 100644
--- a/src/loadSimu.hpp
+++ b/src/loadSimu.hpp
@@ -78,7 +78,7 @@ namespace CosmoTool
 
     ssize_t NumPart;
     ssize_t TotalNumPart;
-    long *Id;
+    int64_t *Id;
     float *Pos[3];
     float *Vel[3];
     float *Mass;