diff --git a/build/remove_old_eduserv_cert.pl b/build/remove_old_eduserv_cert.pl
index 6424d19c..0a3bf999 100755
--- a/build/remove_old_eduserv_cert.pl
+++ b/build/remove_old_eduserv_cert.pl
@@ -7,7 +7,11 @@
 #
 
 # This line indicates that the old certificate is present
-$old_cert_line = 'MIIEiTCCA3GgAwIBAgIRAPzB04tYcniZc/0mSMRCfXgwDQYJKoZIhvcNAQEFBQAw';
+#
+# Ensure that all Base64-encoded characters which affect perl pattern matching are escaped.
+# For example, '+' in the variable indicates 'one or more of the preceding character', 
+# whilst \+ indicates a literal + in the input string.
+$old_cert_line = 'MIIEiDCCA3CgAwIBAgIQOBNA\+hb81eyfqXol6z3klDANBgkqhkiG9w0BAQUFADA2';
 
 while (<>) {