diff --git a/ema_workbench/analysis/prim.py b/ema_workbench/analysis/prim.py
index c24f22ad5..59b000bab 100644
--- a/ema_workbench/analysis/prim.py
+++ b/ema_workbench/analysis/prim.py
@@ -361,7 +361,7 @@ def __init__(self, prim, box_lims, indices):
                    "mean": pd.Series(dtype=float),
                    "res_dim": pd.Series(dtype=int),
                    "mass": pd.Series(dtype=float),
-                   "id": pd.Series(dtype=float)}
+                   "id": pd.Series(dtype=int)}
 
         self.peeling_trajectory = pd.DataFrame(columns)