diff --git a/libtriple/video_td.cpp b/libtriple/video_td.cpp
index 079bfa4..f3dfaa7 100644
--- a/libtriple/video_td.cpp
+++ b/libtriple/video_td.cpp
@@ -942,6 +942,12 @@ bool cVideo::GetScreenImage(unsigned char * &video, int &xres, int &yres, bool g
 		}
 		uint16_t w = *(uint16_t *)(map + WIDTH_OFF);
 		uint16_t h = *(uint16_t *)(map + HEIGHT_OFF);
+		if (w > 720 || h > 576) {
+			lt_info("%s: unhandled resolution %dx%d, is the tuner locked?\n", __func__, w, h);
+			munmap(map, VIDEO_SIZE);
+			close(mfd);
+			return false;
+		}
 		uint8_t *luma, *chroma;
 		int needmem = w * h * 5 / 4; /* chroma is 1/4 in size of luma */
 		int lumasize = w * h;
diff --git a/libtriple/video_td.h b/libtriple/video_td.h
index 8f4893b..f73bb04 100644
--- a/libtriple/video_td.h
+++ b/libtriple/video_td.h
@@ -6,6 +6,8 @@
 //#define video_displayformat_t   vidDispMode_t
 #include "../common/cs_types.h"
 
+#define STB_HAL_VIDEO_HAS_GETSCREENIMAGE 1
+
 typedef enum {
 	ANALOG_SD_RGB_SCART = 0x00,
 	ANALOG_SD_YPRPB_SCART,