diff --git a/src/esp_compat.h b/src/esp_compat.h
index 10a1c56..cfc0d9b 100644
--- a/src/esp_compat.h
+++ b/src/esp_compat.h
@@ -36,8 +36,6 @@ extern TaskHandle_t hcore0, hcore1;
 static inline uint32_t board_millis(void) {
     return ( ( ((uint64_t) xTaskGetTickCount()) * 1000) / configTICK_RATE_HZ );
 }
-#define PICO_UNIQUE_BOARD_ID_SIZE_BYTES 8
-typedef struct { uint8_t id[PICO_UNIQUE_BOARD_ID_SIZE_BYTES]; } pico_unique_board_id_t;
 typedef SemaphoreHandle_t mutex_t;
 typedef SemaphoreHandle_t semaphore_t;
 #define mutex_init(a) do { *(a) = xSemaphoreCreateMutex();} while(0)
diff --git a/src/main.c b/src/main.c
index 930e319..e9dd284 100644
--- a/src/main.c
+++ b/src/main.c
@@ -358,16 +358,19 @@ void core0_loop() {
     }
 }
 
+char pico_serial_str[2 * PICO_UNIQUE_BOARD_ID_SIZE_BYTES + 1];
+pico_unique_board_id_t pico_serial;
 #ifdef ESP_PLATFORM
 #include "tinyusb.h"
 #include "esp_efuse.h"
 #define pico_get_unique_board_id(a) do { uint32_t value; esp_efuse_read_block(EFUSE_BLK1, &value, 0, 32); memcpy((uint8_t *)(a), &value, sizeof(uint32_t)); esp_efuse_read_block(EFUSE_BLK1, &value, 32, 32); memcpy((uint8_t *)(a)+4, &value, sizeof(uint32_t)); } while(0)
 extern const tinyusb_config_t tusb_cfg;
 TaskHandle_t hcore0 = NULL, hcore1 = NULL;
-char pico_serial_str[2 * PICO_UNIQUE_BOARD_ID_SIZE_BYTES + 1];
-pico_unique_board_id_t pico_serial;
 int app_main() {
 #else
+#ifdef ENABLE_EMULATION
+#define pico_get_unique_board_id(a) memset(a, 0, sizeof(*(a)))
+#endif
 int main(void) {
 #endif
     pico_get_unique_board_id(&pico_serial);
diff --git a/src/pico_keys.h b/src/pico_keys.h
index 60b116b..c72ffd7 100644
--- a/src/pico_keys.h
+++ b/src/pico_keys.h
@@ -166,7 +166,11 @@ extern uint32_t button_timeout;
 #define CCID_WRONG_PADDING                   -1011
 #define CCID_VERIFICATION_FAILED             -1012
 
+#if defined(ENABLE_EMULATION) || defined(ESP_PLATFORM)
+#define PICO_UNIQUE_BOARD_ID_SIZE_BYTES 8
+typedef struct { uint8_t id[PICO_UNIQUE_BOARD_ID_SIZE_BYTES]; } pico_unique_board_id_t;
+#endif
 extern pico_unique_board_id_t pico_serial;
-extern char pico_serial_str[];
+extern char pico_serial_str[2 * PICO_UNIQUE_BOARD_ID_SIZE_BYTES + 1];
 
 #endif