diff --git a/src/unix/unix_sdl.c b/src/unix/unix_sdl.c
index 3155a3a1e..a61d338e6 100644
--- a/src/unix/unix_sdl.c
+++ b/src/unix/unix_sdl.c
@@ -133,7 +133,7 @@ sdl_blit_shim(int x, int y, int w, int h)
     params.y = y;
     params.w = w;
     params.h = h;
-    if (!(!sdl_enabled || (h <= 0) || (buffer32 == NULL) || (sdl_render == NULL) || (sdl_tex == NULL))) memcpy(interpixels, &(buffer32->line[y][x]), h * (2048 + 64) * sizeof(uint32_t));
+    if (!(!sdl_enabled || (x < 0) || (y < 0) || (w <= 0) || (h <= 0) || (w > 2048) || (h > 2048) || (buffer32 == NULL) || (sdl_render == NULL) || (sdl_tex == NULL))) memcpy(interpixels, &(buffer32->line[y][x]), h * (2048 + 64) * sizeof(uint32_t));
     blitreq = 1;
     video_blit_complete();
 }
@@ -174,7 +174,7 @@ sdl_blit(int x, int y, int w, int h)
 {
     SDL_Rect r_src;
 
-    if (!sdl_enabled || (h <= 0) || (buffer32 == NULL) || (sdl_render == NULL) || (sdl_tex == NULL)) {
+    if (!sdl_enabled || (x < 0) || (y < 0) || (w <= 0) || (h <= 0) || (w > 2048) || (h > 2048) || (buffer32 == NULL) || (sdl_render == NULL) || (sdl_tex == NULL)) {
     r_src.x = x;
     r_src.y = y;
     r_src.w = w;
diff --git a/src/vnc.c b/src/vnc.c
index f2f4655b0..371e03803 100644
--- a/src/vnc.c
+++ b/src/vnc.c
@@ -172,7 +172,7 @@ vnc_blit(int x, int y, int w, int h)
     uint32_t *p;
     int yy;
 
-    if (h <= 0)
+    if ((x < 0) || (y < 0) || (w <= 0) || (h <= 0) || (w > 2048) || (h > 2048) || (buffer32 == NULL))
 	return;
 
     for (yy=0; yy<h; yy++) {
diff --git a/src/win/win_opengl.c b/src/win/win_opengl.c
index a73ffd981..b2c338a31 100644
--- a/src/win/win_opengl.c
+++ b/src/win/win_opengl.c
@@ -809,9 +809,7 @@ static void opengl_main(void* param)
 
 static void opengl_blit(int x, int y, int w, int h)
 {
-	int yy;
-
-	if ((h <= 0) || (buffer32 == NULL) || (thread == NULL) ||
+	if ((x < 0) || (y < 0) || (w <= 0) || (h <= 0) || (w > 2048) || (h > 2048) || (buffer32 == NULL) || (thread == NULL) ||
 		atomic_flag_test_and_set(&blit_info[write_pos].in_use))
 	{
 		video_blit_complete();
diff --git a/src/win/win_sdl.c b/src/win/win_sdl.c
index ffd589ce0..62a77551b 100644
--- a/src/win/win_sdl.c
+++ b/src/win/win_sdl.c
@@ -234,7 +234,7 @@ sdl_blit(int x, int y, int w, int h)
     SDL_Rect r_src;
     int ret;
 
-    if (!sdl_enabled || (w <= 0) || (h <= 0) || (w > 2048) || (h > 2048) || (buffer32 == NULL) || (sdl_render == NULL) || (sdl_tex == NULL)) {
+    if (!sdl_enabled || (x < 0) || (y < 0) || (w <= 0) || (h <= 0) || (w > 2048) || (h > 2048) || (buffer32 == NULL) || (sdl_render == NULL) || (sdl_tex == NULL)) {
 	video_blit_complete();
 	return;
     }