diff --git a/runtime/Clib/cstring.c b/runtime/Clib/cstring.c
--- a/runtime/Clib/cstring.c
+++ b/runtime/Clib/cstring.c
@@ -31,7 +31,7 @@ string_to_bstring_len( char *c_string, i
 #endif	
    string->string_t.length = len;
 
-   dst = (char *)&(string->string_t.char0);
+   dst = BSTRING_TO_STRING( BSTRING( string ) );
    for( ; len > 0; len-- )
       *dst++ = *c_string++;
   
@@ -83,7 +83,7 @@ make_string( int len, unsigned char c ) 
       string->string_t.length = len;
 
       memset( &(string->string_t.char0), c, len );
-      (&(string->string_t.char0))[ len ] = '\0';
+      STRING_SET( BSTRING( string ), len, '\0' );
 		
       return BSTRING( string );
    }
@@ -105,7 +105,7 @@ make_string_sans_fill( int len ) {
 #endif	
    string->string_t.length = len;
 
-   (&(string->string_t.char0))[ len ] = '\0';
+   STRING_SET( BSTRING( string ), len, '\0' );
 		
    return BSTRING( string );
 }
@@ -183,7 +183,7 @@ c_substring( obj_t src_string, int min, 
    memcpy( &(dst_string->string_t.char0),
 	   &STRING_REF( src_string, min ),
             len );
-   (&(dst_string->string_t.char0))[ len ] = '\0';
+   STRING_SET( BSTRING( dst_string ), len, '\0' );
 
    return BSTRING( dst_string );
 }
diff --git a/runtime/Include/bigloo.h b/runtime/Include/bigloo.h
--- a/runtime/Include/bigloo.h
+++ b/runtime/Include/bigloo.h
@@ -273,7 +273,7 @@ typedef union scmobj {
       header_t        header;    /*  longueur, la chaine C suit.       */
 #endif		
       int             length;
-      unsigned char   char0;
+      unsigned char   char0[ 1 ];
    } string_t;
 
    struct ucs2_string {          /*  Ucs2 strings:                     */