diff --git a/main.c b/main.c
index 0a51c49..4014053 100644
--- a/main.c
+++ b/main.c
@@ -2382,7 +2382,7 @@ static const VNAShellCommand commands[] =
     { "levelchange", cmd_levelchange,    0 },
     { "modulation", cmd_modulation,    0 },
     { "rbw", cmd_rbw,    0 },
-    { "mode", cmd_mode,    0 },
+    { "mode", cmd_mode,    CMD_WAIT_MUTEX },
     { "spur", cmd_spur,    0 },
     { "load", cmd_load,    0 },
     { "offset", cmd_offset, 0},
diff --git a/sa_cmd.c b/sa_cmd.c
index 41717be..212bcfb 100644
--- a/sa_cmd.c
+++ b/sa_cmd.c
@@ -58,14 +58,14 @@ VNA_SHELL_FUNCTION(cmd_mode)
 
 VNA_SHELL_FUNCTION(cmd_modulation )
 {
-  static const char cmd_mod[] = "off|AM|NFM|WFM|extern|freq;
+  static const char cmd_mod[] = "off|am|nfm|wfm|extern|freq";
   if (argc < 1) {
   usage:
     shell_printf("usage: modulation %s 100..6000\r\n", cmd_mod);
     return;
   }
   static const int cmd_mod_val[] = { MO_NONE, MO_AM, MO_NFM, MO_WFM, MO_EXTERNAL, -1};
-  int m = get_str_index(argv[1], cmd_mod);
+  int m = get_str_index(argv[0], cmd_mod);
   if (m<0)
      goto usage;
   if (cmd_mod_val[m] >=0)