diff --git a/algs4/extract-jars b/algs4/extract-jars
index 0e4c0da..7d3b965 100755
--- a/algs4/extract-jars
+++ b/algs4/extract-jars
@@ -4,7 +4,9 @@ set -e
 set -x
 
 cd src/java
-chmod 644 *.java *.class
+set +e
+chmod 644 *.java *.class 2>/dev/null
+set -e
 jar xf ../../algs4.jar
 jar xf ../../stdlib.jar
 rm stdlib.jar