diff --git a/xorriso/parse_exec.c b/xorriso/parse_exec.c
index 42543d84..8d29e072 100644
--- a/xorriso/parse_exec.c
+++ b/xorriso/parse_exec.c
@@ -1778,7 +1778,7 @@ next_command:;
      ret= Xorriso_stop_msg_watcher(xorriso, 0);
      fprintf(stderr, "xorriso -test: Xorriso_stop_msg_watcher() = %d\n", ret);
 
-   } else if(strcmp(arg1, "parse") == 0) {
+   } else if(strcmp(arg1, "parse") == 0 || strcmp(arg1, "nullparse") == 0) {
      (*idx)+= 5;
      pline= "";
      if(*idx - 5 < argc)
@@ -1795,7 +1795,8 @@ next_command:;
      pflag= 0;
      if(*idx - 1 < argc)
        sscanf(argv[*idx - 1], "%d", &pflag);
-     ret= Xorriso_parse_line(xorriso, pline, prefix, separators, max_words,
+     ret= Xorriso_parse_line(strcmp(arg1, "nullparse") == 0 ? NULL : xorriso, 
+                             pline, prefix, separators, max_words,
                              &pargc, &pargv, pflag);
      fprintf(stderr,
         "xorriso_test: Xorriso_parse_line: ret= %d , argc= %d , argv= 0x%lX\n",
@@ -1909,13 +1910,17 @@ int Xorriso_parse_line(struct XorrisO *xorriso, char *line,
                        int *argc, char ***argv, int flag)
 {
  int ret, bsl_mode;
- char *to_parse;
+ char *to_parse, *progname= "";
+
+ if(xorriso == NULL && (flag & (32 | 64))) {
+   ret= -2; goto ex;
+ }
 
  *argc= 0;
  *argv= NULL;
 
  to_parse= line;
- if(flag & 1)
+ if((flag & 1) || xorriso == NULL)
    bsl_mode= (flag >> 1) & 3;
  else
    bsl_mode= xorriso->bsl_interpretation & 3;
@@ -1927,18 +1932,23 @@ int Xorriso_parse_line(struct XorrisO *xorriso, char *line,
    }
  }
 
- ret= Sfile_sep_make_argv(xorriso->progname, to_parse, separators,
+ if(xorriso != NULL)
+   progname= xorriso->progname;
+ ret= Sfile_sep_make_argv(progname, to_parse, separators,
                           max_words, argc, argv,
                           (!(flag & 32)) | 4 | (bsl_mode << 5));
  if(ret < 0) {
-   Xorriso_msgs_submit(xorriso, 0,
-      "Severe lack of resources during command line parsing", 0, "FATAL", 0);
-   goto ex;
+   if(xorriso != NULL)
+     Xorriso_msgs_submit(xorriso, 0,
+        "Severe lack of resources during command line parsing", 0, "FATAL", 0);
+   ret= -1; goto ex;
  }
  if(ret == 0) {
-   sprintf(xorriso->info_text, "Incomplete quotation in %s line: %s",
-           (flag & 32) ? "command" : "parsed", to_parse);
-   Xorriso_msgs_submit(xorriso, 0, xorriso->info_text, 0, "FAILURE", 0);
+   if((flag & 64) && xorriso != NULL) {
+     sprintf(xorriso->info_text, "Incomplete quotation in %s line: %s",
+             (flag & 32) ? "command" : "parsed", to_parse);
+     Xorriso_msgs_submit(xorriso, 0, xorriso->info_text, 0, "FAILURE", 0);
+   }
    goto ex;
  }
  ret= 1;
diff --git a/xorriso/xorriso.h b/xorriso/xorriso.h
index afc26bf5..ef0a9e78 100644
--- a/xorriso/xorriso.h
+++ b/xorriso/xorriso.h
@@ -364,8 +364,18 @@ int Xorriso_execute_option(struct XorrisO *xorriso, char *line, int flag);
 /* Parse a text line into words. This parsing obeys the same rules as
    command line parsing but allows to skip a prefix, to use a user provided
    set of separator characters, and to restrict the number of parsed words.
+
+   If parameter xorriso is NULL, then this call is safe for usage by
+   a concurrent thread while a xorriso API call is being executed.
+
    @since 1.2.6
    @param xorriso     The context object which provides settings for parsing
+                      and output channels for error messages.
+                      May be NULL in order to allow concurrent execution e.g.
+                      by a callback function of Xorriso_start_msg_watcher().
+                      If xorriso is NULL then:
+                        flag bit1-bit4 are in effect even if bit0 is not set.
+                        flag bit5 and bit6 may not be set.
    @param line        A text of one or more words according to man xorriso
                       paragraph "Command processing" up to and including
                       "Backslash Interpretation".
@@ -391,8 +401,8 @@ int Xorriso_execute_option(struct XorrisO *xorriso, char *line, int flag);
                       Do not forget to dispose the allocated memory by a
                       call to Xorriso__dispose_words().
    @param flag        Bitfield for control purposes
-                      bit0=   Override setting of -backslash_codes
-                      bit1-4= With bit1: backslash behavior
+                      bit0=   Override setting of -backslash_codes.
+                      bit1-4= With bit0: backslash behavior
                               0= off
                               1= in_double_quotes
                               2= in_quotes
@@ -400,10 +410,13 @@ int Xorriso_execute_option(struct XorrisO *xorriso, char *line, int flag);
                       bit5=   Prepend the program name as (*argv)[0], so that
                               *argv is suitable for Xorriso_interpreter()
                               and other calls which expect this.
+                              Not allowed if xorriso is NULL.
                       bit6=   Issue failure message in case of return 0
+                              Not allowed if xorriso is NULL.
    @return            <=0 means error and invalidity of *argv:
                               0 = Input format error. E.g. bad quotation mark.
                              -1 = Lack of resources. E.g. memory.
+                             -2 = Improper combination of call parameters.
                       >0 means success but not necessarily a valid result:
                               1 = Result in argc and argv is valid (but may
                                   be empty by argc == 0, argv == NULL).
diff --git a/xorriso/xorriso_timestamp.h b/xorriso/xorriso_timestamp.h
index e86103c7..b7b32510 100644
--- a/xorriso/xorriso_timestamp.h
+++ b/xorriso/xorriso_timestamp.h
@@ -1 +1 @@
-#define Xorriso_timestamP "2012.10.02.134601"
+#define Xorriso_timestamP "2012.10.03.124152"