diff --git a/pym/portage/checksum.py b/pym/portage/checksum.py
index 73e01b5..90260b4 100644
--- a/pym/portage/checksum.py
+++ b/pym/portage/checksum.py
@@ -301,8 +301,9 @@ def perform_checksum(filename, hashname="MD5", calc_prelink=0):
 				prelink_capable = False
 		try:
 			if hashname not in hashfunc_map:
-				raise portage.exception.DigestException(hashname + \
-					" hash function not available (needs dev-python/pycrypto)")
+				raise portage.exception.DigestException(
+					"% hash function not available (needs dev-python/pycrypto)"
+						% hashname )
 			myhash, mysize = hashfunc_map[hashname](myfilename)
 		except (OSError, IOError) as e:
 			if e.errno in (errno.ENOENT, errno.ESTALE):