diff --git a/src/pylorax/images.py b/src/pylorax/images.py
index 6e92833c..768e0081 100644
--- a/src/pylorax/images.py
+++ b/src/pylorax/images.py
@@ -193,7 +193,7 @@ class PPC(object):
             dst = joinpaths(self.outputroot, ppcdir, "yaboot.conf")
             yabootconf = cpfile(self.reqs["yabootconf"], dst)
 
-            replace(yabootconf, r"%BITS%", bits)
+            replace(yabootconf, r"%BITS%", str(bits))
             replace(yabootconf, r"%PRODUCT%", self.product)
             replace(yabootconf, r"%VERSION%", self.version)