diff --git a/src/ukify/ukify.py b/src/ukify/ukify.py
index 5b8bf96974c..335de994d88 100755
--- a/src/ukify/ukify.py
+++ b/src/ukify/ukify.py
@@ -441,7 +441,8 @@ def join_initrds(initrds):
     seq = []
     for file in initrds:
         initrd = file.read_bytes()
-        padding = b'\0' * round_up(len(initrd), 4)  # pad to 32 bit alignment
+        n = len(initrd)
+        padding = b'\0' * (round_up(n, 4) - n)  # pad to 32 bit alignment
         seq += [initrd, padding]
 
     return b''.join(seq)