diff --git a/cmd/pxe_utils.c b/cmd/pxe_utils.c
index 235522f4bb..b9d9a5786c 100644
--- a/cmd/pxe_utils.c
+++ b/cmd/pxe_utils.c
@@ -322,7 +322,8 @@ static int label_localboot(struct pxe_label *label)
 	if (label->append) {
 		char bootargs[CONFIG_SYS_CBSIZE];
 
-		cli_simple_process_macros(label->append, bootargs);
+		cli_simple_process_macros(label->append, bootargs,
+					  sizeof(bootargs));
 		env_set("bootargs", bootargs);
 	}
 
@@ -430,7 +431,8 @@ static int label_boot(struct cmd_tbl *cmdtp, struct pxe_label *label)
 		strcat(bootargs, ip_str);
 		strcat(bootargs, mac_str);
 
-		cli_simple_process_macros(bootargs, finalbootargs);
+		cli_simple_process_macros(bootargs, finalbootargs,
+					  sizeof(finalbootargs));
 		env_set("bootargs", finalbootargs);
 		printf("append: %s\n", finalbootargs);
 	}
diff --git a/common/cli_simple.c b/common/cli_simple.c
index 7d91316a0f..e80ba488a5 100644
--- a/common/cli_simple.c
+++ b/common/cli_simple.c
@@ -60,13 +60,14 @@ int cli_simple_parse_line(char *line, char *argv[])
 	return nargs;
 }
 
-void cli_simple_process_macros(const char *input, char *output)
+int cli_simple_process_macros(const char *input, char *output, int max_size)
 {
 	char c, prev;
 	const char *varname_start = NULL;
 	int inputcnt = strlen(input);
-	int outputcnt = CONFIG_SYS_CBSIZE;
+	int outputcnt = max_size;
 	int state = 0;		/* 0 = waiting for '$'  */
+	int ret;
 
 	/* 1 = waiting for '(' or '{' */
 	/* 2 = waiting for ')' or '}' */
@@ -157,13 +158,18 @@ void cli_simple_process_macros(const char *input, char *output)
 		prev = c;
 	}
 
-	if (outputcnt)
+	ret = inputcnt ? -ENOSPC : 0;
+	if (outputcnt) {
 		*output = 0;
-	else
+	} else {
 		*(output - 1) = 0;
+		ret = -ENOSPC;
+	}
 
 	debug_parser("[PROCESS_MACROS] OUTPUT len %zd: \"%s\"\n",
 		     strlen(output_start), output_start);
+
+	return ret;
 }
 
  /*
@@ -239,7 +245,8 @@ int cli_simple_run_command(const char *cmd, int flag)
 		debug_parser("token: \"%s\"\n", token);
 
 		/* find macros in this token and replace them */
-		cli_simple_process_macros(token, finaltoken);
+		cli_simple_process_macros(token, finaltoken,
+					  sizeof(finaltoken));
 
 		/* Extract arguments */
 		argc = cli_simple_parse_line(finaltoken, argv);
diff --git a/include/cli.h b/include/cli.h
index 39b913743b..3449fa6ae7 100644
--- a/include/cli.h
+++ b/include/cli.h
@@ -34,8 +34,10 @@ int cli_simple_run_command(const char *cmd, int flag);
  *
  * @param input		Input string possible containing $() / ${} vars
  * @param output	Output string with $() / ${} vars expanded
+ * @param max_size	Maximum size of @output (including terminator)
+ * @return 0 if OK, -ENOSPC if we ran out of space in @output
  */
-void cli_simple_process_macros(const char *input, char *output);
+int cli_simple_process_macros(const char *input, char *output, int max_size);
 
 /**
  * cli_simple_run_command_list() - Execute a list of command