diff --git a/focus_seq_FLI.py b/focus_seq_FLI.py
index 5907ac9..4f4218f 100755
--- a/focus_seq_FLI.py
+++ b/focus_seq_FLI.py
@@ -71,7 +71,7 @@ def get_image(filename, exp_time):
         "-r",
         "/tmp/10micron.fitsheader",
         "-x",
-        "{:d}".format(np.round(exp_time * 1000)),  # to microseconds
+        "{:d}".format(int(np.round(exp_time * 1000))),  # to microseconds
         fname,
     ]