diff --git a/32blit-pico/board/vgaboard/config.cmake b/32blit-pico/board/vgaboard/config.cmake
index 4dea17220..7b3463b50 100644
--- a/32blit-pico/board/vgaboard/config.cmake
+++ b/32blit-pico/board/vgaboard/config.cmake
@@ -1,6 +1,7 @@
 set(BLIT_BOARD_NAME "VGA Board")
 
 set(BLIT_BOARD_DEFINITIONS
+    PICO_AUDIO_I2S_BUFFER_SAMPLE_LENGTH=256
     PICO_SCANVIDEO_PLANE1_VARIABLE_FRAGMENT_DMA=1
     PICO_SCANVIDEO_MAX_SCANLINE_BUFFER_WORDS=12
 )
diff --git a/32blit-pico/display_scanvideo.cpp b/32blit-pico/display_scanvideo.cpp
index 00982028d..f2ddf5878 100644
--- a/32blit-pico/display_scanvideo.cpp
+++ b/32blit-pico/display_scanvideo.cpp
@@ -13,9 +13,6 @@ static volatile int buf_index = 0;
 
 static volatile bool do_render = true;
 
-// user render function
-void render(uint32_t);
-
 static bool do_render_soon = false; // slightly delayed to handle the queue
 
 static void fill_scanline_buffer(struct scanvideo_scanline_buffer *buffer) {
diff --git a/32blit-pico/main.cpp b/32blit-pico/main.cpp
index e744fce85..018ec44b4 100644
--- a/32blit-pico/main.cpp
+++ b/32blit-pico/main.cpp
@@ -32,7 +32,9 @@ static uint32_t random() {
 }
 
 static void debug(const char *message) {
-  fputs(message, stdout);
+  auto p = message;
+  while(*p)
+    putchar(*p++);
 
   usb_debug(message);
 }
diff --git a/32blit-sdl/Audio.cpp b/32blit-sdl/Audio.cpp
index 49ff6b6f5..38dab6702 100644
--- a/32blit-sdl/Audio.cpp
+++ b/32blit-sdl/Audio.cpp
@@ -9,6 +9,8 @@
 
 blit::AudioChannel channels[CHANNEL_COUNT];
 
+static void _audio_callback(void *userdata, uint8_t *stream, int len);
+
 Audio::Audio() {
     blit::api.channels = channels;
 
@@ -35,7 +37,7 @@ Audio::~Audio() {
     SDL_CloseAudioDevice(audio_device);
 }
 
-void _audio_bufferfill(short *buffer, int buffer_size){
+static void _audio_bufferfill(short *buffer, int buffer_size){
     memset(buffer, 0, buffer_size);
 
     for(auto sample = 0; sample < buffer_size; sample++){
@@ -43,6 +45,6 @@ void _audio_bufferfill(short *buffer, int buffer_size){
     }
 }
 
-void _audio_callback(void *userdata, uint8_t *stream, int len){
+static void _audio_callback(void *userdata, uint8_t *stream, int len){
     _audio_bufferfill((short *)stream, len / 2);
 }
diff --git a/32blit-sdl/Audio.hpp b/32blit-sdl/Audio.hpp
index 9efed2e26..0f01037fe 100644
--- a/32blit-sdl/Audio.hpp
+++ b/32blit-sdl/Audio.hpp
@@ -8,6 +8,3 @@ class Audio {
 
         SDL_AudioDeviceID audio_device;
 };
-
-void _audio_bufferfill(short *pBuffer, int pBufferSize);
-void _audio_callback(void *userdata, uint8_t *stream, int len);