diff --git a/Core/apu.c b/Core/apu.c
index 4ff7664d..6a54518d 100755
--- a/Core/apu.c
+++ b/Core/apu.c
@@ -283,7 +283,7 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
                     }
                 }
                 gb->apu.is_active[GB_WAVE] = true;
-                gb->apu.wave_channel.pulse_length = ~gb->io_registers[GB_IO_NR31];
+                gb->apu.wave_channel.pulse_length = (~gb->io_registers[GB_IO_NR31]) * 2;
                 gb->apu.wave_channel.sample_countdown = gb->apu.wave_channel.sample_length + 3;
                 gb->apu.wave_channel.current_sample_index = 0;
                 /* Note that we don't change the sample just yet! This was verified on hardware. */
diff --git a/Core/apu.h b/Core/apu.h
index 6690a588..88117fb9 100644
--- a/Core/apu.h
+++ b/Core/apu.h
@@ -11,8 +11,8 @@
 #define CH_STEP (MAX_CH_AMP/0xF/7)
 #endif
 
-/* Lengths are in either DIV ticks (256Hz, triggered by the DIV register) or
-   APU ticks (2MHz, triggered by an internal APU clock)*/
+/* Lengths are in either DIV ticks (512Hz, triggered by the DIV register) or
+   APU ticks (2MHz, triggered by an internal APU clock) */
 
 typedef struct
 {