diff --git a/src/libflate/deflate.c b/src/libflate/deflate.c
index 15a186a..ceaa77f 100644
--- a/src/libflate/deflate.c
+++ b/src/libflate/deflate.c
@@ -1132,6 +1132,8 @@
 	Chain *c;
 	int i, m, em, bits;
 
+	memset(&cs, 0, sizeof cs);
+
 	/*
 	 * set up the sorted list of leaves
 	 */