diff --git a/lib/fluent/config/literal_parser.rb b/lib/fluent/config/literal_parser.rb
index d165c728ff..c30f752de9 100644
--- a/lib/fluent/config/literal_parser.rb
+++ b/lib/fluent/config/literal_parser.rb
@@ -98,11 +98,11 @@ def scan_double_quoted_string
             else
               return string.join
             end
-          elsif check(/[^"]#{LINE_END_WITHOUT_SPACING_AND_COMMENT}/)
-            if s = check(/[^\\]#{LINE_END_WITHOUT_SPACING_AND_COMMENT}/)
+          elsif check(/[^"]#{LINE_END_WITHOUT_SPACING_AND_COMMENT}/o)
+            if s = check(/[^\\]#{LINE_END_WITHOUT_SPACING_AND_COMMENT}/o)
               string << s
             end
-            skip(/[^"]#{LINE_END_WITHOUT_SPACING_AND_COMMENT}/)
+            skip(/[^"]#{LINE_END_WITHOUT_SPACING_AND_COMMENT}/o)
           elsif s = scan(/\\./)
             string << eval_escape_char(s[1,1])
           elsif skip(/\#\{/)
diff --git a/lib/fluent/config/v1_parser.rb b/lib/fluent/config/v1_parser.rb
index d8806c9377..7666d3d8cd 100644
--- a/lib/fluent/config/v1_parser.rb
+++ b/lib/fluent/config/v1_parser.rb
@@ -83,7 +83,7 @@ def parse_element(root_element, elem_name, attrs = {}, elems = [])
           elsif skip(/\</)
             e_name = scan(ELEMENT_NAME)
             spacing
-            e_arg = scan_string(/(?:#{ZERO_OR_MORE_SPACING}\>)/)
+            e_arg = scan_string(/(?:#{ZERO_OR_MORE_SPACING}\>)/o)
             spacing
             unless skip(/\>/)
               parse_error! "expected '>'"
@@ -98,7 +98,7 @@ def parse_element(root_element, elem_name, attrs = {}, elems = [])
             new_e.v1_config = true
             elems << new_e
 
-          elsif root_element && skip(/(\@include|include)#{SPACING}/)
+          elsif root_element && skip(/(\@include|include)#{SPACING}/o)
             if !prev_match.start_with?('@')
               @logger.warn "'include' is deprecated. Use '@include' instead" if @logger
             end