diff --git a/Core/apu.c b/Core/apu.c
index 2525931..c42e6df 100644
--- a/Core/apu.c
+++ b/Core/apu.c
@@ -1000,16 +1000,17 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
                 else {
                     unsigned extra_delay = 0;
                     if (gb->model == GB_MODEL_CGB_E /* || gb->model == GB_MODEL_CGB_D */) {
-                       if ((!(value & 4) && ((gb->io_registers[reg] & 4) || old_sample_length == 0x3FF)) ||
-                           (old_sample_length == 0x7FF && gb->apu.square_channels[index].sample_length != 0x7FF)) {
+                        if (!(value & 4) && !(((gb->apu.square_channels[index].sample_countdown - 1) / 2) & 0x400)) {
                             gb->apu.square_channels[index].current_sample_index++;
                             gb->apu.square_channels[index].current_sample_index &= 0x7;
-                       }
-                       else if (gb->apu.square_channels[index].sample_length == 0x7FF &&
-                                old_sample_length != 0x7FF &&
-                                (gb->apu.square_channels[index].current_sample_index & 0x80)) {
-                           extra_delay += 2;
-                       }
+                            gb->apu.is_active[index] = true;
+                        }
+                        /* Todo: verify with the schematics what's going on in here */
+                        else if (gb->apu.square_channels[index].sample_length == 0x7FF &&
+                                 old_sample_length != 0x7FF &&
+                                 (gb->apu.square_channels[index].current_sample_index & 0x80)) {
+                            extra_delay += 2;
+                        }
                     }
                     /* Timing quirk: if already active, sound starts 2 (2MHz) ticks earlier.*/
                     gb->apu.square_channels[index].sample_countdown = (gb->apu.square_channels[index].sample_length ^ 0x7FF) * 2 + 4 - gb->apu.lf_div + extra_delay;