diff --git a/plot.c b/plot.c
index 29cf357..20be44f 100644
--- a/plot.c
+++ b/plot.c
@@ -24,7 +24,7 @@
 #include "nanovna.h"
 
 #pragma GCC push_options
-#pragma GCC optimize ("Og")      // Makes the code just a bit faster, disable during debugging.
+#pragma GCC optimize ("Os")      // Makes the code just a bit faster, disable during debugging.
 
 #ifdef __SCROLL__
 uint16_t _grid_y = (CHART_BOTTOM / NGRIDY);
diff --git a/sa_core.c b/sa_core.c
index 7ac9b0c..d1d280d 100644
--- a/sa_core.c
+++ b/sa_core.c
@@ -7069,6 +7069,7 @@ void self_test(int test)
     goto quit;
   }
 #endif
+  setting.external_gain = 0;                  // Must be 0
 //  set_sweep_points(POINTS_COUNT);
   if (test == 0) {
     if (test_wait ) {