diff --git a/main.c b/main.c
index 0049333..9152c5f 100644
--- a/main.c
+++ b/main.c
@@ -194,9 +194,7 @@ static THD_FUNCTION(Thread1, arg)
       if (uistat.marker_tracking) {
         int i = marker_search_max(active_marker);
         if (i != -1 && active_marker != MARKER_INVALID) {
-          markers[active_marker].index = i;
-          markers[active_marker].frequency = getFrequency(i);
-
+          set_marker_index(active_marker, i);
           redraw_request |= REDRAW_MARKER;
         }
       }
@@ -1066,7 +1064,7 @@ VNA_SHELL_FUNCTION(cmd_hop)
 #endif
 
 static void
-update_marker_index(void)
+update_markers_index(void)
 {
   int m, idx;
   freq_t fstart = get_sweep_frequency(ST_START);
@@ -1092,11 +1090,18 @@ update_marker_index(void)
       idx = r * (sweep_points-1);
 #endif
     }
-    markers[m].index = idx;
-    markers[m].frequency = getFrequency(idx);
+    set_marker_index(m, idx);
   }
 }
 
+void
+set_marker_index(int m, int16_t idx)
+{
+  if ((uint32_t)m >= MARKERS_MAX || (uint16_t)idx >= sweep_points) return;
+  markers[m].index = idx;
+  markers[m].frequency = getFrequency(idx);
+}
+
 void set_marker_frequency(int m, freq_t f)
 {
   if (m == MARKER_INVALID || !markers[m].enabled)
@@ -1182,7 +1187,7 @@ update_frequencies(void)
   set_frequencies(start, stop, sweep_points);
   // operation_requested|= OP_FREQCHANGE;
 
-  update_marker_index();
+  update_markers_index();
 
   // set grid layout
   update_grid();
@@ -1491,8 +1496,7 @@ VNA_SHELL_FUNCTION(cmd_marker)
     case 2: markers[t].enabled = TRUE; active_marker = t;
       int i = marker_search_max(active_marker);
       if (i == -1) i = 0;
-      markers[active_marker].index = i;
-      markers[active_marker].frequency = getFrequency(i);
+      set_marker_index(active_marker, i);
       goto display_marker;
     default:
       // select active marker and move to index or frequency
@@ -1502,10 +1506,8 @@ VNA_SHELL_FUNCTION(cmd_marker)
       active_marker = t;
       if (value > sweep_points)
         set_marker_frequency(active_marker, value);
-      else {
-        markers[t].index = value;
-        markers[t].frequency = getFrequency(value);
-      }
+      else
+        set_marker_index(t, value);
       return;
   }
  usage:
diff --git a/nanovna.h b/nanovna.h
index 95f66b8..bd4d319 100644
--- a/nanovna.h
+++ b/nanovna.h
@@ -205,6 +205,7 @@ void send_buffer(uint8_t * buf, int s);
 #endif
 void set_marker_frequency(int m, freq_t f);
 void set_marker_time(int m, float f);
+void set_marker_index(int m, int16_t idx);
 void toggle_sweep(void);
 void toggle_mute(void);
 void toggle_pulse(void);
diff --git a/sa_core.c b/sa_core.c
index 4f32dbe..f9392c1 100644
--- a/sa_core.c
+++ b/sa_core.c
@@ -4478,8 +4478,7 @@ static volatile int dummy;
     }
     while (m < MARKERS_MAX) {                  // Insufficient maxima found
       if (markers[m].enabled && markers[m].mtype & M_TRACKING) {    // More available markers found
-        markers[m].index = 0;                             // Enabled but no max so set to left most frequency
-        markers[m].frequency = getFrequency(0);
+        set_marker_index(m, 0); // Enabled but no max so set to left most frequency
       }
       m++;                              // Try next marker
     }
@@ -4517,35 +4516,28 @@ static volatile int dummy;
       if (r < l) {
         l = markers[1].index;
         r = markers[0].index;
-        markers[0].index = l;
-        markers[1].index = r;
       }
-      freq_t lf = getFrequency(l);
-      freq_t rf = getFrequency(r);
-      markers[0].frequency = lf;
-      markers[1].frequency = rf;
-
+      set_marker_index(0, l);
+      set_marker_index(1, r);
+      freq_t lf = markers[0].frequency;
+      freq_t rf = markers[1].frequency;
       markers[2].enabled = search_maximum(2, lf - (rf - lf), 12);
       markers[3].enabled = search_maximum(3, rf + (rf - lf), 12);
     } else if (setting.measurement == M_PHASE_NOISE  && markers[0].index > 10) {    //  ------------Phase noise measurement
-      markers[1].index =  markers[0].index + (setting.mode == M_LOW ? WIDTH/4 : -WIDTH/4);  // Position phase noise marker at requested offset
-      markers[1].frequency = getFrequency(markers[1].index);
+      // Position phase noise marker at requested offset
+      set_marker_index(1, markers[0].index + (setting.mode == M_LOW ? WIDTH/4 : -WIDTH/4));
     } else if ((setting.measurement == M_PASS_BAND || setting.measurement == M_FM)  && markers[0].index > 10) {      // ----------------Pass band measurement
       int t = 0;
       float v = actual_t[markers[0].index] - (in_selftest ? 6.0 : 3.0);
       while (t < markers[0].index && actual_t[t+1] < v)                                        // Find left -3dB point
         t++;
-      if (t< markers[0].index) {
-        markers[1].index = t;
-        markers[1].frequency = getFrequency(t);
-      }
+      if (t< markers[0].index)
+        set_marker_index(1, t);
       t = setting._sweep_points-1;;
       while (t > markers[0].index && actual_t[t-1] < v)                // find right -3dB point
         t--;
-      if (t > markers[0].index) {
-        markers[2].index = t;
-        markers[2].frequency = getFrequency(t);
-      }
+      if (t > markers[0].index)
+        set_marker_index(2, t);
     } else if (setting.measurement == M_AM) {      // ----------------AM measurement
       if (S_IS_AUTO(setting.agc )) {
 #ifdef __SI4432__
diff --git a/ui_sa.c b/ui_sa.c
index 1142b86..77767f9 100644
--- a/ui_sa.c
+++ b/ui_sa.c
@@ -1563,7 +1563,7 @@ static UI_FUNCTION_ADV_CALLBACK(menu_marker_select_acb)
   }
   markers[data-1].enabled = true;
 //  interpolate_maximum(data-1);        // possibly not a maximum
-  markers[data-1].frequency = getFrequency(markers[data-1].index);
+  set_marker_index(data-1, markers[data-1].index);
   active_marker_select(data-1);
   menu_push_submenu(menu_marker_modify);
   redraw_marker(active_marker);
@@ -1649,7 +1649,7 @@ static UI_FUNCTION_ADV_CALLBACK(menu_marker_ref_select_acb)
   }
   markers[data-1].enabled = true;
 //  interpolate_maximum(data-1);        // possibly not a maximum
-  markers[data-1].frequency = getFrequency(markers[data-1].index);
+  set_marker_index(data-1, markers[data-1].index);
   markers[active_marker].ref = data-1;
   redraw_marker(active_marker);
   menu_move_back(false);