diff --git a/combine-extra-source b/combine-extra-source
index 32888f3..7d85191 100755
--- a/combine-extra-source
+++ b/combine-extra-source
@@ -1,5 +1,6 @@
 #!/bin/bash
 
+set -e
 set -x
 
 base="${1?Usage: $0 base-name}"