diff -Naurp a/src/giffunc.c b/src/giffunc.c
--- a/src/giffunc.c	2021-09-20 13:19:00.000000000 +0200
+++ b/src/giffunc.c	2024-02-04 14:05:47.811880522 +0100
@@ -466,8 +466,10 @@ Gif_CopyImage(Gif_Image *src)
 void Gif_MakeImageEmpty(Gif_Image* gfi) {
     Gif_ReleaseUncompressedImage(gfi);
     Gif_ReleaseCompressedImage(gfi);
-    gfi->left = gfi->top = 0;
-    gfi->width = gfi->height = 1;
+    gfi->left = gfi->left < 0xFFFE ? gfi->left : 0xFFFE;
+    gfi->top = gfi->top < 0xFFFE ? gfi->top : 0xFFFE;
+    gfi->width = 1;
+    gfi->height = 1;
     gfi->transparent = 0;
     Gif_CreateUncompressedImage(gfi, 0);
     gfi->img[0][0] = 0;
diff -Naurp a/src/support.c b/src/support.c
--- a/src/support.c	2023-06-14 17:47:12.000000000 +0200
+++ b/src/support.c	2024-02-04 14:05:51.307885109 +0100
@@ -1421,9 +1421,9 @@ analyze_crop(int nmerger, Gt_Crop* crop,
         }
       }
 
-    if (t > b)
+    if (t > b) {
       crop->w = crop->h = 0;
-    else {
+    } else {
       crop->x = l;
       crop->y = t;
       crop->w = r - l;
@@ -1618,7 +1618,8 @@ merge_frame_interval(Gt_Frameset *fset,
       desti->comment = 0;
     }
     if (fr->comment) {
-      if (!desti->comment) desti->comment = Gif_NewComment();
+      if (!desti->comment)
+        desti->comment = Gif_NewComment();
       merge_comments(desti->comment, fr->comment);
       /* delete the comment early to help with memory; set field to 0 so we
          don't re-free it later */
@@ -1628,10 +1629,22 @@ merge_frame_interval(Gt_Frameset *fset,
 
     if (fr->interlacing >= 0)
       desti->interlace = fr->interlacing;
-    if (fr->left >= 0)
-      desti->left = fr->left + (fr->position_is_offset ? desti->left : 0);
-    if (fr->top >= 0)
-      desti->top = fr->top + (fr->position_is_offset ? desti->top : 0);
+    if (fr->left >= 0) {
+      int left = fr->left + (fr->position_is_offset ? desti->left : 0);
+      if (left + desti->width > 65535) {
+        error(1, "left position %d out of range", left);
+        return 0;
+      }
+      desti->left = left;
+    }
+    if (fr->top >= 0) {
+      int top = fr->top + (fr->position_is_offset ? desti->top : 0);
+      if (top + desti->height > 65535) {
+        error(1, "top position %d out of range", top);
+        return 0;
+      }
+      desti->top = top;
+    }
 
     if (fr->delay >= 0)
       desti->delay = fr->delay;
diff -Naurp a/src/xform.c b/src/xform.c
--- a/src/xform.c	2023-06-14 17:48:05.000000000 +0200
+++ b/src/xform.c	2024-02-04 14:05:47.812880524 +0100
@@ -262,18 +262,18 @@ crop_image(Gif_Image* gfi, Gt_Frame* fr,
             gfi->img[j] = old_img[c.y + j] + c.x;
         gfi->img[c.h] = 0;
         Gif_DeleteArray(old_img);
+        gfi->left += c.x - fr->left_offset;
+        gfi->top += c.y - fr->top_offset;
         gfi->width = c.w;
         gfi->height = c.h;
-    } else if (preserve_total_crop)
+    } else if (preserve_total_crop) {
         Gif_MakeImageEmpty(gfi);
-    else {
+    } else {
         Gif_DeleteArray(gfi->img);
         gfi->img = 0;
         gfi->width = gfi->height = 0;
     }
 
-    gfi->left += c.x - fr->left_offset;
-    gfi->top += c.y - fr->top_offset;
     return gfi->img != 0;
 }