diff --git a/calculate_rmsd b/calculate_rmsd
index 12b6323..0f5c87e 100755
--- a/calculate_rmsd
+++ b/calculate_rmsd
@@ -9,7 +9,6 @@ license: https://github.com/charnley/rmsd/blob/master/LICENSE
 
 """
 
-import argparse
 import numpy as np
 import re
 
@@ -200,6 +199,7 @@ def get_coordinates(filename, ignore_hydrogens=False):
 
 
 if __name__ == "__main__":
+    import argparse
 
     description = """
 Calculate Root-mean-square deviation (RMSD) between structure A and B, in XYZ format.