diff --git a/Bugzilla/DB/Oracle.pm b/Bugzilla/DB/Oracle.pm
index 9e8c16e72..a68d25351 100644
--- a/Bugzilla/DB/Oracle.pm
+++ b/Bugzilla/DB/Oracle.pm
@@ -119,7 +119,7 @@ sub sql_group_concat {
   my ($self, $text, $separator) = @_;
   $separator = $self->quote(', ') if !defined $separator;
   my ($distinct, $rest) = $text =~ /^(\s*DISTINCT\s|)(.+)$/i;
-  return "group_concat($distinct T_CLOB_DELIM(NVL($rest, ' '), $separator))";
+  return "group_concat($distinct T_CLOB_DELIM(NVL(TO_CHAR($rest), ' '), $separator))";
 }
 
 sub sql_regexp {