diff --git a/plot_transmission_timeline.py b/plot_transmission_timeline.py
index 19b781d..d03007f 100755
--- a/plot_transmission_timeline.py
+++ b/plot_transmission_timeline.py
@@ -199,9 +199,9 @@ if __name__ == "__main__":
             i += 1
 
     cmap = matplotlib.cm.get_cmap("Set3")
-    for cell_id in transmission_df["cellID"].unique():
-        bounds = transmission_df[["index", "cellID"]].groupby("cellID").agg(["min", "max"]).loc[cell_id]
-        host.axvspan(bounds.min(), bounds.max(), alpha=0.3, color=cmap.colors[color_dict[cell_id]])
+    for c in transmission_df["cellID"].unique():
+        bounds = transmission_df[["index", "cellID"]].groupby("cellID").agg(["min", "max"]).loc[c]
+        host.axvspan(bounds.min(), bounds.max(), alpha=0.3, color=cmap.colors[color_dict[c]])
 
     plt.subplots_adjust()