diff --git a/read_in.py b/read_in.py
index f65b4a0..afffe5f 100644
--- a/read_in.py
+++ b/read_in.py
@@ -41,7 +41,7 @@ def read_single_elevation(dat: str) -> Result[int, str]:
 		try_(replace(dat), float, dat)
 	)
 
-def read_elevation_line(line: str) -> Result[Iterator[int], Tuple[int, str]]:
+def read_elevation_line(line: str) -> Result[Sequence[int], Tuple[int, str]]:
 	"""
 	Reads a line of elevations
 
@@ -168,7 +168,7 @@ class UnrecognizedColor(NamedTuple):
     y: int
     "The y coordinate of the unidentifided color"
 
-def load_gb_pixels_as_map(pixels: Iterable[Tuple[int, int]]) -> Result[Iterator[Terrain], UnrecognizedColor]:
+def load_gb_pixels_as_map(pixels: Iterable[Tuple[int, int]]) -> Result[Sequence[Terrain], UnrecognizedColor]:
     """
     Interpret the green and blue bands of an image as pixels on a map
 
@@ -192,7 +192,7 @@ def load_gb_pixels_as_map(pixels: Iterable[Tuple[int, int]]) -> Result[Iterator[
         for (pix_no, gb) in enumerate(pixels)
     ])
 
-def load_image(path: str) -> Result[List[Terrain], UnrecognizedColor]:
+def load_image(path: str) -> Result[Sequence[Terrain], UnrecognizedColor]:
     "Run `load_gb_pixels_as_map` on an image read from a path"
     with Image.open(path) as im:
         return load_gb_pixels_as_map(zip(im.getdata(1), im.getdata(2)))