diff --git a/Core/apu.c b/Core/apu.c
index 319ab369b..2c9f1e22f 100644
--- a/Core/apu.c
+++ b/Core/apu.c
@@ -1752,6 +1752,7 @@ void GB_apu_write(GB_gameboy_t *gb, uint8_t reg, uint8_t value)
 
 void GB_set_sample_rate(GB_gameboy_t *gb, unsigned sample_rate)
 {
+    GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
     gb->apu_output.sample_rate = sample_rate;
     if (sample_rate) {
         gb->apu_output.highpass_rate = pow(0.999958, GB_get_clock_rate(gb) / (double)sample_rate);
@@ -1764,7 +1765,7 @@ void GB_set_sample_rate(GB_gameboy_t *gb, unsigned sample_rate)
 
 void GB_set_sample_rate_by_clocks(GB_gameboy_t *gb, double cycles_per_sample)
 {
-
+    GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
     if (cycles_per_sample == 0) {
         GB_set_sample_rate(gb, 0);
         return;
diff --git a/Core/camera.c b/Core/camera.c
index cbfc494e3..d6e61447d 100644
--- a/Core/camera.c
+++ b/Core/camera.c
@@ -110,11 +110,17 @@ uint8_t GB_camera_read_image(GB_gameboy_t *gb, uint16_t addr)
 
 void GB_set_camera_get_pixel_callback(GB_gameboy_t *gb, GB_camera_get_pixel_callback_t callback)
 {
+    if (!callback) {
+        GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+    }
     gb->camera_get_pixel_callback = callback;
 }
 
 void GB_set_camera_update_request_callback(GB_gameboy_t *gb, GB_camera_update_request_callback_t callback)
 {
+    if (!callback) {
+        GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+    }
     if (gb->camera_countdown > 0 && callback) {
         GB_log(gb, "Camera update request callback set while camera was proccessing, clearing camera countdown.\n");
         gb->camera_countdown = 0;
diff --git a/Core/display.c b/Core/display.c
index 889dbc3a9..1d377c3b6 100644
--- a/Core/display.c
+++ b/Core/display.c
@@ -42,11 +42,17 @@ const GB_palette_t *GB_get_palette(GB_gameboy_t *gb)
 
 void GB_set_vblank_callback(GB_gameboy_t *gb, GB_vblank_callback_t callback)
 {
+    if (!callback) {
+        GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+    }
     gb->vblank_callback = callback;
 }
 
 void GB_set_rgb_encode_callback(GB_gameboy_t *gb, GB_rgb_encode_callback_t callback)
 {
+    if (!callback) {
+        GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+    }
     
     gb->rgb_encode_callback = callback;
     GB_update_dmg_palette(gb);
diff --git a/Core/gb.c b/Core/gb.c
index c4398d3b2..91ec43d76 100644
--- a/Core/gb.c
+++ b/Core/gb.c
@@ -836,6 +836,8 @@ int GB_save_battery_size(GB_gameboy_t *gb)
 
 int GB_save_battery_to_buffer(GB_gameboy_t *gb, uint8_t *buffer, size_t size)
 {
+    GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+
     if (!gb->cartridge_type->has_battery) return 0; // Nothing to save.
     if (gb->cartridge_type->mbc_type == GB_TPP1 && !(gb->rom[0x153] & 8)) return 0; // Nothing to save.
     if (gb->mbc_ram_size == 0 && !gb->cartridge_type->has_rtc) return 0; /* Claims to have battery, but has no RAM or RTC */
@@ -1241,12 +1243,18 @@ uint32_t *GB_get_pixels_output(GB_gameboy_t *gb)
 
 void GB_set_log_callback(GB_gameboy_t *gb, GB_log_callback_t callback)
 {
+    if (!callback) {
+        GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+    }
     gb->log_callback = callback;
 }
 
 void GB_set_input_callback(GB_gameboy_t *gb, GB_input_callback_t callback)
 {
 #ifndef GB_DISABLE_DEBUGGER
+    if (!callback) {
+        GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+    }
     if (gb->input_callback == default_input_callback) {
         gb->async_input_callback = NULL;
     }
@@ -1257,27 +1265,42 @@ void GB_set_input_callback(GB_gameboy_t *gb, GB_input_callback_t callback)
 void GB_set_async_input_callback(GB_gameboy_t *gb, GB_input_callback_t callback)
 {
 #ifndef GB_DISABLE_DEBUGGER
+    if (!callback) {
+        GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+    }
     gb->async_input_callback = callback;
 #endif
 }
 
 void GB_set_execution_callback(GB_gameboy_t *gb, GB_execution_callback_t callback)
 {
+    if (!callback) {
+        GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+    }
     gb->execution_callback = callback;
 }
 
 void GB_set_lcd_line_callback(GB_gameboy_t *gb, GB_lcd_line_callback_t callback)
 {
+    if (!callback) {
+        GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+    }
     gb->lcd_line_callback = callback;
 }
 
 void GB_set_lcd_status_callback(GB_gameboy_t *gb, GB_lcd_status_callback_t callback)
 {
+    if (!callback) {
+        GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+    }
     gb->lcd_status_callback = callback;
 }
 
 void GB_set_infrared_callback(GB_gameboy_t *gb, GB_infrared_callback_t callback)
 {
+    if (!callback) {
+        GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+    }
     gb->infrared_callback = callback;
 }
 
@@ -1288,16 +1311,25 @@ void GB_set_infrared_input(GB_gameboy_t *gb, bool state)
 
 void GB_set_rumble_callback(GB_gameboy_t *gb, GB_rumble_callback_t callback)
 {
+    if (!callback) {
+        GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+    }
     gb->rumble_callback = callback;
 }
 
 void GB_set_serial_transfer_bit_start_callback(GB_gameboy_t *gb, GB_serial_transfer_bit_start_callback_t callback)
 {
+    if (!callback) {
+        GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+    }
     gb->serial_transfer_bit_start_callback = callback;
 }
 
 void GB_set_serial_transfer_bit_end_callback(GB_gameboy_t *gb, GB_serial_transfer_bit_end_callback_t callback)
 {
+    if (!callback) {
+        GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+    }
     gb->serial_transfer_bit_end_callback = callback;
 }
 
@@ -1341,6 +1373,7 @@ void GB_serial_set_data_bit(GB_gameboy_t *gb, bool data)
 
 void GB_disconnect_serial(GB_gameboy_t *gb)
 {
+    GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
     gb->serial_transfer_bit_start_callback = NULL;
     gb->serial_transfer_bit_end_callback = NULL;
     
@@ -1941,22 +1974,34 @@ double GB_get_usual_frame_rate(GB_gameboy_t *gb)
 
 void GB_set_joyp_write_callback(GB_gameboy_t *gb, GB_joyp_write_callback_t callback)
 {
+    if (!callback) {
+        GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+    }
     gb->joyp_write_callback = callback;
 }
 
 void GB_set_icd_pixel_callback(GB_gameboy_t *gb, GB_icd_pixel_callback_t callback)
 {
+    if (!callback) {
+        GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+    }
     gb->icd_pixel_callback = callback;
 }
 
 void GB_set_icd_hreset_callback(GB_gameboy_t *gb, GB_icd_hreset_callback_t callback)
 {
+    if (!callback) {
+        GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+    }
     gb->icd_hreset_callback = callback;
 }
 
 
 void GB_set_icd_vreset_callback(GB_gameboy_t *gb, GB_icd_vreset_callback_t callback)
 {
+    if (!callback) {
+        GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+    }
     gb->icd_vreset_callback = callback;
 }
 
diff --git a/Core/joypad.c b/Core/joypad.c
index 460cdda23..d91391de6 100644
--- a/Core/joypad.c
+++ b/Core/joypad.c
@@ -224,5 +224,8 @@ void GB_set_emulate_joypad_bouncing(GB_gameboy_t *gb, bool emulate)
 
 void GB_set_update_input_hint_callback(GB_gameboy_t *gb, GB_update_input_hint_callback_t callback)
 {
+    if (!callback) {
+        GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+    }
     gb->update_input_hint_callback = callback;
 }
diff --git a/Core/memory.c b/Core/memory.c
index e10b7bf9c..77024233b 100644
--- a/Core/memory.c
+++ b/Core/memory.c
@@ -767,6 +767,9 @@ static read_function_t *const read_map[] =
 
 void GB_set_read_memory_callback(GB_gameboy_t *gb, GB_read_memory_callback_t callback)
 {
+    if (!callback) {
+        GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+    }
     gb->read_memory_callback = callback;
 }
 
@@ -1781,6 +1784,9 @@ static write_function_t *const write_map[] =
 
 void GB_set_write_memory_callback(GB_gameboy_t *gb, GB_write_memory_callback_t callback)
 {
+    if (!callback) {
+        GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
+    }
     gb->write_memory_callback = callback;
 }
 
diff --git a/Core/printer.c b/Core/printer.c
index 005f452b2..3b86b5c01 100644
--- a/Core/printer.c
+++ b/Core/printer.c
@@ -214,6 +214,7 @@ static bool serial_end(GB_gameboy_t *gb)
 
 void GB_connect_printer(GB_gameboy_t *gb, GB_print_image_callback_t callback, GB_printer_done_callback_t done_callback)
 {
+    GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
     memset(&gb->printer, 0, sizeof(gb->printer));
     GB_set_serial_transfer_bit_start_callback(gb, serial_start);
     GB_set_serial_transfer_bit_end_callback(gb, serial_end);
diff --git a/Core/workboy.c b/Core/workboy.c
index d5e2b72f7..2315c8402 100644
--- a/Core/workboy.c
+++ b/Core/workboy.c
@@ -143,6 +143,7 @@ void GB_connect_workboy(GB_gameboy_t *gb,
                         GB_workboy_set_time_callback_t set_time_callback,
                         GB_workboy_get_time_callback_t get_time_callback)
 {
+    GB_ASSERT_NOT_RUNNING_OTHER_THREAD(gb)
     memset(&gb->workboy, 0, sizeof(gb->workboy));
     GB_set_serial_transfer_bit_start_callback(gb, serial_start);
     GB_set_serial_transfer_bit_end_callback(gb, serial_end);