diff --git a/prody/proteins/ciffile.py b/prody/proteins/ciffile.py
index f5a2195bc..e714ebec5 100644
--- a/prody/proteins/ciffile.py
+++ b/prody/proteins/ciffile.py
@@ -19,8 +19,6 @@
 from .cifheader import getCIFHeaderDict
 from .header import buildBiomolecules, assignSecstr, isHelix, isSheet
 
-from string import ascii_uppercase
-
 __all__ = ['parseMMCIFStream', 'parseMMCIF', 'parseCIF']