diff --git a/qpdf/qtest/qpdf/diff-encrypted b/qpdf/qtest/qpdf/diff-encrypted
index 64c0b2a..a68822e 100755
--- a/qpdf/qtest/qpdf/diff-encrypted
+++ b/qpdf/qtest/qpdf/diff-encrypted
@@ -1,6 +1,6 @@
 #!/bin/sh
 lines=$(expr + $(diff $1 $2 | egrep '^[<>]' | egrep -v 'Date' | wc -l))
-if [ "$lines" == "0" ]; then
+if [ "$lines" = "0" ]; then
    echo okay
 else
    diff -a -U 0 $1 $2