diff --git a/addons/ot/src/parser.c b/addons/ot/src/parser.c
index c7522e942..5dec8629d 100644
--- a/addons/ot/src/parser.c
+++ b/addons/ot/src/parser.c
@@ -189,7 +189,7 @@ static const char *flt_ot_parse_invalid_char(const char *name, int type)
  */
 static int flt_ot_parse_cfg_check(const char *file, int linenum, char **args, const void *id, const struct flt_ot_parse_data *parse_data, size_t parse_data_size, const struct flt_ot_parse_data **pdata, char **err)
 {
-	int i, retval = ERR_NONE;
+	int i, argc, retval = ERR_NONE;
 
 	FLT_OT_FUNC("\"%s\", %d, %p, %p, %p, %zu, %p:%p, %p:%p", file, linenum, args, id, parse_data, parse_data_size, FLT_OT_DPTR_ARGS(pdata), FLT_OT_DPTR_ARGS(err));
 
@@ -197,12 +197,15 @@ static int flt_ot_parse_cfg_check(const char *file, int linenum, char **args, co
 
 	*pdata = NULL;
 
+	/* First check here if args[0] is the correct keyword. */
 	for (i = 0; (*pdata == NULL) && (i < parse_data_size); i++)
 		if (strcmp(parse_data[i].name, args[0]) == 0)
 			*pdata = parse_data + i;
 
 	if (*pdata == NULL)
 		FLT_OT_PARSE_ERR(err, "'%s' : unknown keyword", args[0]);
+	else
+		argc = flt_ot_args_count(args);
 
 	if ((retval & ERR_CODE) || (id == NULL))
 		/* Do nothing. */;
@@ -214,20 +217,16 @@ static int flt_ot_parse_cfg_check(const char *file, int linenum, char **args, co
 	 * line than is required.
 	 */
 	if (!(retval & ERR_CODE))
-		for (i = 1; i < (*pdata)->args_min; i++)
-			if (!FLT_OT_ARG_ISVALID(i))
-				FLT_OT_PARSE_ERR(err, "'%s' : too few arguments (use '%s%s')", args[0], (*pdata)->name, (*pdata)->usage);
+		if (argc < (*pdata)->args_min)
+			FLT_OT_PARSE_ERR(err, "'%s' : too few arguments (use '%s%s')", args[0], (*pdata)->name, (*pdata)->usage);
 
 	/*
 	 * Checking that more arguments are specified in the configuration
 	 * line than the maximum allowed.
 	 */
-	if (!(retval & ERR_CODE) && ((*pdata)->args_max > 0)) {
-		for ( ; (i <= (*pdata)->args_max) && FLT_OT_ARG_ISVALID(i); i++);
-
-		if (i > (*pdata)->args_max)
+	if (!(retval & ERR_CODE) && ((*pdata)->args_max > 0))
+		if (argc > (*pdata)->args_max)
 			FLT_OT_PARSE_ERR(err, "'%s' : too many arguments (use '%s%s')", args[0], (*pdata)->name, (*pdata)->usage);
-	}
 
 	/* Checking that the first argument has only allowed characters. */
 	if (!(retval & ERR_CODE) && ((*pdata)->check_name > 0)) {
diff --git a/addons/ot/src/util.c b/addons/ot/src/util.c
index 3adc5a300..f6812bcc2 100644
--- a/addons/ot/src/util.c
+++ b/addons/ot/src/util.c
@@ -37,13 +37,13 @@
  */
 void flt_ot_args_dump(char **args)
 {
-	int i, n;
+	int i, argc;
 
-	for (n = 1; FLT_OT_ARG_ISVALID(n); n++);
+	argc = flt_ot_args_count(args);
 
-	(void)fprintf(stderr, FLT_OT_DBG_FMT("%.*sargs[%d]: { '%s' "), dbg_indent_level, FLT_OT_DBG_INDENT, n, args[0]);
+	(void)fprintf(stderr, FLT_OT_DBG_FMT("%.*sargs[%d]: { '%s' "), dbg_indent_level, FLT_OT_DBG_INDENT, argc, args[0]);
 
-	for (i = 1; FLT_OT_ARG_ISVALID(i); i++)
+	for (i = 1; i < argc; i++)
 		(void)fprintf(stderr, "'%s' ", args[i]);
 
 	(void)fprintf(stderr, "}\n");
@@ -365,10 +365,30 @@ ssize_t flt_ot_chunk_add(struct buffer *chk, const void *src, size_t n, char **e
  */
 int flt_ot_args_count(char **args)
 {
-	int retval = 0;
+	int i, retval = 0;
 
-	if (args != NULL)
-		for ( ; FLT_OT_ARG_ISVALID(retval); retval++);
+	if (args == NULL)
+		return retval;
+
+	/*
+	 * It is possible that some arguments within the configuration line
+	 * are not specified; that is, they are set to a blank string.
+	 *
+	 * For example:
+	 *   keyword '' arg_2
+	 *
+	 * In that case the content of the args field will be like this:
+	 *   args[0]:                  'keyword'
+	 *   args[1]:                  NULL pointer
+	 *   args[2]:                  'arg_2'
+	 *   args[3 .. MAX_LINE_ARGS): NULL pointers
+	 *
+	 * The total number of arguments is the index of the last argument
+	 * (increased by 1) that is not a NULL pointer.
+	 */
+	for (i = 0; i < MAX_LINE_ARGS; i++)
+		if (FLT_OT_ARG_ISVALID(i))
+			retval = i + 1;
 
 	return retval;
 }
@@ -391,13 +411,15 @@ int flt_ot_args_count(char **args)
  */
 void flt_ot_args_to_str(char **args, int idx, char **str)
 {
-	int i;
+	int i, argc;
 
 	if ((args == NULL) || (*args == NULL))
 		return;
 
-	for (i = idx; FLT_OT_ARG_ISVALID(i); i++)
-		(void)memprintf(str, "%s%s%s", (*str == NULL) ? "" : *str, (i == idx) ? "" : " ", args[i]);
+	argc = flt_ot_args_count(args);
+
+	for (i = idx; i < argc; i++)
+		(void)memprintf(str, "%s%s%s", (*str == NULL) ? "" : *str, (i == idx) ? "" : " ", (args[i] == NULL) ? "" : args[i]);
 }