diff --git a/contrib/examples/simpleover.c b/contrib/examples/simpleover.c
index c226af6627..d19cc31a48 100644
--- a/contrib/examples/simpleover.c
+++ b/contrib/examples/simpleover.c
@@ -186,8 +186,11 @@ sprite_op(const struct sprite *sprite, int x_offset, int y_offset,
                   out_pixel[3] = in_pixel[3];
                }
             }
-         } while (++x < image->width);
-      } while (++y < image->height);
+         /* Stop at the right edge of the sprite; the input is truncated to
+          * the sprite area rather than written beyond sprite->buffer.
+          */
+         } while (++x < image->width && (unsigned)(x + x_offset) < sprite->width);
+      } while (++y < image->height && (unsigned)(y + y_offset) < sprite->height);
    }
 }