diff --git a/dstat_interface/experiments/experiment_template.py b/dstat_interface/experiments/experiment_template.py
index ee1587e151482543373965331740a92d12c7ee81..3cc2d6612c468f267fe21ab9377616e12a83bff9 100755
--- a/dstat_interface/experiments/experiment_template.py
+++ b/dstat_interface/experiments/experiment_template.py
@@ -282,7 +282,7 @@ class PlotBox(object):
         # Calculate size of grid needed
         
         if len(self.plotnames) > 1:
-            gs = gridspec.GridSpec(ceil(len(self.plotnames)/2.),2)
+            gs = gridspec.GridSpec(int(ceil(len(self.plotnames)/2.)),2)
         else:
             gs = gridspec.GridSpec(1,1)
         for n, i in enumerate(self.plotnames):