diff --git a/include/gfx/main.hpp b/include/gfx/main.hpp
index e4bedb13..32bc4802 100644
--- a/include/gfx/main.hpp
+++ b/include/gfx/main.hpp
@@ -40,6 +40,8 @@ struct Options {
 		uint16_t top;
 		uint16_t width;
 		uint16_t height;
+		uint32_t right() const { return left + width * 8; }
+		uint32_t bottom() const { return top + height * 8; }
 	} inputSlice{0, 0, 0, 0};                          // -L (margins in clockwise order, like CSS)
 	std::array<uint16_t, 2> maxNbTiles{UINT16_MAX, 0}; // -N
 	uint16_t nbPalettes = 8;                           // -n
diff --git a/src/gfx/main.cpp b/src/gfx/main.cpp
index 9de3857e..1c50c4b7 100644
--- a/src/gfx/main.cpp
+++ b/src/gfx/main.cpp
@@ -863,7 +863,7 @@ int main(int argc, char *argv[]) {
 		}
 		fprintf(
 		    stderr,
-		    "\tInput image slice: %" PRIu32 "x%" PRIu32 " pixels starting at (%" PRId32 ", %" PRId32
+		    "\tInput image slice: %" PRIu16 "x%" PRIu16 " pixels starting at (%" PRIu16 ", %" PRIu16
 		    ")\n",
 		    options.inputSlice.width,
 		    options.inputSlice.height,
diff --git a/src/gfx/process.cpp b/src/gfx/process.cpp
index 369a4c86..826d585b 100644
--- a/src/gfx/process.cpp
+++ b/src/gfx/process.cpp
@@ -226,6 +226,30 @@ public:
 		if (options.inputSlice.height == 0 && height % 8 != 0) {
 			fatal("Image height (%" PRIu32 " pixels) is not a multiple of 8!", height);
 		}
+		if (options.inputSlice.right() > width || options.inputSlice.bottom() > height) {
+			error(
+			    "Image slice ((%" PRIu16 ", %" PRIu16 ") to (%" PRIu32 ", %" PRIu32
+			    ")) is outside the image bounds (%" PRIu32 "x%" PRIu32 ")!",
+			    options.inputSlice.left,
+			    options.inputSlice.top,
+			    options.inputSlice.right(),
+			    options.inputSlice.bottom(),
+			    width,
+			    height
+			);
+			if (options.inputSlice.width % 8 == 0 && options.inputSlice.height % 8 == 0) {
+				fprintf(
+				    stderr,
+				    "note: Did you mean the slice \"%" PRIu32 ",%" PRIu32 ":%" PRId32 ",%" PRId32
+				    "\"? (width and height are in tiles, not pixels!)\n",
+				    options.inputSlice.left,
+				    options.inputSlice.top,
+				    options.inputSlice.width / 8,
+				    options.inputSlice.height / 8
+				);
+			}
+			giveUp();
+		}
 
 		pixels.resize(static_cast<size_t>(width) * static_cast<size_t>(height));
 
diff --git a/test/gfx/bad_slice.err b/test/gfx/bad_slice.err
new file mode 100644
index 00000000..f3f7e357
--- /dev/null
+++ b/test/gfx/bad_slice.err
@@ -0,0 +1,3 @@
+error: Image slice ((2, 2) to (130, 130)) is outside the image bounds (20x20)!
+note: Did you mean the slice "2,2:2,2"? (width and height are in tiles, not pixels!)
+Conversion aborted after 1 error
diff --git a/test/gfx/bad_slice.flags b/test/gfx/bad_slice.flags
new file mode 100644
index 00000000..f55c2775
--- /dev/null
+++ b/test/gfx/bad_slice.flags
@@ -0,0 +1 @@
+-L 2,2:16,16
diff --git a/test/gfx/bad_slice.png b/test/gfx/bad_slice.png
new file mode 100644
index 00000000..8a0bd2d5
Binary files /dev/null and b/test/gfx/bad_slice.png differ
diff --git a/test/gfx/oob_slice_wh.err b/test/gfx/oob_slice_wh.err
new file mode 100644
index 00000000..b49ccf3f
--- /dev/null
+++ b/test/gfx/oob_slice_wh.err
@@ -0,0 +1,2 @@
+error: Image slice ((2, 2) to (34, 18)) is outside the image bounds (20x20)!
+Conversion aborted after 1 error
diff --git a/test/gfx/oob_slice_wh.flags b/test/gfx/oob_slice_wh.flags
new file mode 100644
index 00000000..d820a521
--- /dev/null
+++ b/test/gfx/oob_slice_wh.flags
@@ -0,0 +1 @@
+-L 2,2:4,2
diff --git a/test/gfx/oob_slice_wh.png b/test/gfx/oob_slice_wh.png
new file mode 100644
index 00000000..8a0bd2d5
Binary files /dev/null and b/test/gfx/oob_slice_wh.png differ
diff --git a/test/gfx/oob_slice_xy.err b/test/gfx/oob_slice_xy.err
new file mode 100644
index 00000000..9a9e02ed
--- /dev/null
+++ b/test/gfx/oob_slice_xy.err
@@ -0,0 +1,2 @@
+error: Image slice ((2, 99) to (10, 107)) is outside the image bounds (20x20)!
+Conversion aborted after 1 error
diff --git a/test/gfx/oob_slice_xy.flags b/test/gfx/oob_slice_xy.flags
new file mode 100644
index 00000000..2cd08ba5
--- /dev/null
+++ b/test/gfx/oob_slice_xy.flags
@@ -0,0 +1 @@
+-L 2,99:1,1
diff --git a/test/gfx/oob_slice_xy.png b/test/gfx/oob_slice_xy.png
new file mode 100644
index 00000000..8a0bd2d5
Binary files /dev/null and b/test/gfx/oob_slice_xy.png differ