diff --git a/csdr/csdr.py b/csdr/csdr.py
index 1b1f361..8915fdc 100644
--- a/csdr/csdr.py
+++ b/csdr/csdr.py
@@ -490,8 +490,10 @@ class dsp(object):
         return self.secondary_demodulator
 
     def set_secondary_fft_size(self, secondary_fft_size):
-        # to change this, restart is required
+        if self.secondary_fft_size == secondary_fft_size:
+            return
         self.secondary_fft_size = secondary_fft_size
+        self.restart()
 
     def set_audio_compression(self, what):
         if self.audio_compression == what:
@@ -640,6 +642,8 @@ class dsp(object):
         return self.demodulator
 
     def set_fft_size(self, fft_size):
+        if self.fft_size == fft_size:
+            return
         self.fft_size = fft_size
         self.restart()
 
diff --git a/htdocs/openwebrx.js b/htdocs/openwebrx.js
index 07bcf25..92cf973 100644
--- a/htdocs/openwebrx.js
+++ b/htdocs/openwebrx.js
@@ -779,9 +779,12 @@ function on_ws_recv(evt) {
                         break;
                     case "secondary_config":
                         var s = json['value'];
-                        window.secondary_fft_size = s['secondary_fft_size'];
-                        window.secondary_bw = s['secondary_bw'];
-                        window.if_samp_rate = s['if_samp_rate'];
+                        if ('secondary_fft_size' in s)
+                            window.secondary_fft_size = s['secondary_fft_size'];
+                        if ('secondary_bw' in s)
+                            window.secondary_bw = s['secondary_bw'];
+                        if ('if_samp_rate' in s)
+                            window.if_samp_rate = s['if_samp_rate'];
                         secondary_demod_init_canvases();
                         break;
                     case "receiver_details":
diff --git a/owrx/dsp.py b/owrx/dsp.py
index 647d28c..ec96b70 100644
--- a/owrx/dsp.py
+++ b/owrx/dsp.py
@@ -137,21 +137,25 @@ class DspManager(csdr.output, SdrSourceEventClient):
 
         if self.props["digimodes_enable"]:
 
+            def send_secondary_config(*args):
+                self.handler.write_secondary_dsp_config(
+                    {
+                        "secondary_fft_size": self.props["digimodes_fft_size"],
+                        "if_samp_rate": self.dsp.if_samp_rate(),
+                        "secondary_bw": self.dsp.secondary_bw(),
+                    }
+                )
+
             def set_secondary_mod(mod):
                 if mod == False:
                     mod = None
                 self.dsp.set_secondary_demodulator(mod)
                 if mod is not None:
-                    self.handler.write_secondary_dsp_config(
-                        {
-                            "secondary_fft_size": self.props["digimodes_fft_size"],
-                            "if_samp_rate": self.dsp.if_samp_rate(),
-                            "secondary_bw": self.dsp.secondary_bw(),
-                        }
-                    )
+                    send_secondary_config()
 
             self.subscriptions += [
                 self.props.wireProperty("secondary_mod", set_secondary_mod),
+                self.props.wireProperty("digimodes_fft_size", send_secondary_config),
                 self.props.wireProperty("secondary_offset_freq", self.dsp.set_secondary_offset_freq),
             ]