diff --git a/mysql-test/lib/mtr_cases.pm b/mysql-test/lib/mtr_cases.pm
index 52872fa610f..dc385cb6c78 100644
--- a/mysql-test/lib/mtr_cases.pm
+++ b/mysql-test/lib/mtr_cases.pm
@@ -1036,7 +1036,7 @@ sub get_tags_from_file($$) {
     }
 
     # Check for a sourced include file.
-    if ($line =~ /^(--)?[[:space:]]*source[[:space:]]+([^;[:space:]]+)/)
+    if ($line =~ /^[[:space:]]*(--)?[[:space:]]*source[[:space:]]+([^;[:space:]]+)/)
     {
       my $include= $2;
       # The rules below must match open_file() function of mysqltest.cc