diff --git a/common.cpp b/common.cpp
index 17e7348b4..424e97dd5 100644
--- a/common.cpp
+++ b/common.cpp
@@ -607,16 +607,16 @@ const wchar_t *wsetlocale(int category, const wchar_t *locale)
 	return (wchar_t *)setlocale_buff->buff;	
 }
 
-int contains_internal( const wchar_t *a, ... )
+bool contains_internal( const wchar_t *a, ... )
 {
-	wchar_t *arg;
+	const wchar_t *arg;
 	va_list va;
 	int res = 0;
 
 	CHECK( a, 0 );
 	
 	va_start( va, a );
-	while( (arg=va_arg(va, wchar_t *) )!= 0 ) 
+	while( (arg=va_arg(va, const wchar_t *) )!= 0 ) 
 	{
 		if( wcscmp( a,arg) == 0 )
 		{
@@ -626,7 +626,28 @@ int contains_internal( const wchar_t *a, ... )
 		
 	}
 	va_end( va );
-	return res;	
+	return res;
+}
+
+/* wcstring variant of contains_internal. The first parameter is a wcstring, the rest are const wchar_t* */
+__sentinel bool contains_internal( const wcstring &needle, ... )
+{
+	const wchar_t *arg;
+	va_list va;
+	int res = 0;
+
+	va_start( va, needle );
+	while( (arg=va_arg(va, const wchar_t *) )!= 0 ) 
+	{
+		if( needle == arg)
+		{
+			res=1;
+			break;
+		}
+		
+	}
+	va_end( va );
+	return res;
 }
 
 int read_blocked(int fd, void *buf, size_t count)
diff --git a/common.h b/common.h
index 88fc4ca76..23eee113d 100644
--- a/common.h
+++ b/common.h
@@ -440,7 +440,8 @@ const wchar_t *wsetlocale( int category, const wchar_t *locale );
 
    \return zero if needle is not found, of if needle is null, non-zero otherwise
 */
-__sentinel int contains_internal( const wchar_t *needle, ... );
+__sentinel bool contains_internal( const wchar_t *needle, ... );
+__sentinel bool contains_internal( const wcstring &needle, ... );
 
 /**
    Call read while blocking the SIGCHLD signal. Should only be called
diff --git a/highlight.cpp b/highlight.cpp
index de20fde33..c1d2f3839 100644
--- a/highlight.cpp
+++ b/highlight.cpp
@@ -646,7 +646,7 @@ void tokenize( const wchar_t * const buff, int * const color, const int pos, arr
 						int mark = tok_get_pos( &tok );
 						color[ tok_get_pos( &tok ) ] = HIGHLIGHT_COMMAND;
 						
-						if( parser_keywords_is_subcommand( cmd.c_str() ) )
+						if( parser_keywords_is_subcommand( cmd ) )
 						{
 							
 							int sw;
@@ -668,7 +668,7 @@ void tokenize( const wchar_t * const buff, int * const color, const int pos, arr
 							
 							sw = parser_keywords_is_switch( tok_last( &tok ) );
 							
-							if( !parser_keywords_is_block( cmd.c_str() ) &&
+							if( !parser_keywords_is_block( cmd ) &&
 							   sw == ARG_SWITCH )
 							{
 								/* 
diff --git a/parser.cpp b/parser.cpp
index f2a52e3a4..b526251e6 100644
--- a/parser.cpp
+++ b/parser.cpp
@@ -1887,7 +1887,7 @@ int parser_t::parse_job( process_t *p,
 				builtin_exists(args->at(0).completion.c_str()))
 			{
 				p->type = INTERNAL_BUILTIN;
-				is_new_block |= parser_keywords_is_block( args->at( 0 ).completion.c_str() );
+				is_new_block |= parser_keywords_is_block( args->at( 0 ).completion );
 			}
 		}
 		
diff --git a/parser_keywords.cpp b/parser_keywords.cpp
index 6b9ce0c73..2e3487024 100644
--- a/parser_keywords.cpp
+++ b/parser_keywords.cpp
@@ -14,15 +14,15 @@ Functions having to do with parser keywords, like testing if a function is a blo
 #include "parser_keywords.h"
 
 
-int parser_keywords_is_switch( const wchar_t *cmd )
+bool parser_keywords_is_switch( const wcstring &cmd )
 {
-	if( wcscmp( cmd, L"--" ) == 0 )
+	if( cmd == L"--" )
 		return ARG_SKIP;
 	else 
-		return cmd[0] == L'-';
+		return ! cmd.empty() && cmd.at(0) == L'-';
 }
 
-int parser_keywords_skip_arguments( const wchar_t *cmd )
+bool parser_keywords_skip_arguments( const wcstring &cmd )
 {
 	return contains( cmd,
 					 L"else",
@@ -30,7 +30,7 @@ int parser_keywords_skip_arguments( const wchar_t *cmd )
 }
 
 
-int parser_keywords_is_subcommand( const wchar_t *cmd )
+bool parser_keywords_is_subcommand( const wcstring &cmd )
 {
 
 	return parser_keywords_skip_arguments( cmd ) ||
@@ -46,7 +46,7 @@ int parser_keywords_is_subcommand( const wchar_t *cmd )
 	
 }
 
-int parser_keywords_is_block( const wchar_t *word)
+bool parser_keywords_is_block( const wcstring &word)
 {
 	return contains( word,
 					 L"for",
@@ -57,7 +57,7 @@ int parser_keywords_is_block( const wchar_t *word)
 					 L"begin" );
 }
 
-int parser_keywords_is_reserved( const wchar_t *word)
+bool parser_keywords_is_reserved( const wcstring &word)
 {
 	return parser_keywords_is_block(word) ||
 		parser_keywords_is_subcommand( word ) ||
diff --git a/parser_keywords.h b/parser_keywords.h
index e8212334c..c2cc15d97 100644
--- a/parser_keywords.h
+++ b/parser_keywords.h
@@ -23,7 +23,7 @@ enum
    Check if the specified argument is a switch. Return ARG_SWITCH if yes,
    ARG_NON_SWITCH if no and ARG_SKIP if the argument is '--'
 */
-int parser_keywords_is_switch( const wchar_t *cmd );
+bool parser_keywords_is_switch( const wcstring &cmd );
 
 
 /**
@@ -33,7 +33,7 @@ int parser_keywords_is_switch( const wchar_t *cmd );
    \return 1 of the command parameter is a command, 0 otherwise
 */
 
-int parser_keywords_is_subcommand( const wchar_t *cmd );
+bool parser_keywords_is_subcommand( const wcstring &cmd );
 
 /**
    Tests if the specified command is a reserved word, i.e. if it is
@@ -44,20 +44,20 @@ int parser_keywords_is_subcommand( const wchar_t *cmd );
    \param word The command name to test
    \return 1 of the command parameter is a command, 0 otherwise
 */
-int parser_keywords_is_reserved( const wchar_t *word );
+bool parser_keywords_is_reserved( const wcstring &word );
 
 /**
    Test if the specified string is command that opens a new block
 */
 
-int parser_keywords_is_block( const wchar_t *word);
+bool parser_keywords_is_block( const wcstring &word);
 
 /**
    Check if the specified command is one of the builtins that cannot
    have arguments, any followin argument is interpreted as a new
    command
 */
-int parser_keywords_skip_arguments( const wchar_t *cmd );
+bool parser_keywords_skip_arguments( const wcstring &cmd );
 
 
 #endif