diff --git a/lib/trinity/sim_file.ex b/lib/trinity/sim_file.ex
index 301b3b5..e85ff56 100644
--- a/lib/trinity/sim_file.ex
+++ b/lib/trinity/sim_file.ex
@@ -126,8 +126,8 @@ defmodule Trinity.SimFile do
     start_bin_size = min(bytes, @block_size - start_pos)
 
     <<
-      _prefix::binary-size(start_pos),
-      bin_acc::binary-size(start_bin_size),
+      _prefix::binary-size(^start_pos),
+      bin_acc::binary-size(^start_bin_size),
       _::binary,
     >> = read_block(file_data, fd, start_block_index)
 
@@ -143,7 +143,7 @@ defmodule Trinity.SimFile do
   defp do_read_blocks(file_data, fd, block_index, bin_acc, bytes_remaining) when bytes_remaining < @block_size do
     assert bytes_remaining > 0
     <<
-      bin::binary-size(bytes_remaining),
+      bin::binary-size(^bytes_remaining),
       _rest::binary,
     >> = read_block(file_data, fd, block_index)
     <<bin_acc::binary, bin::binary>>
@@ -175,7 +175,7 @@ defmodule Trinity.SimFile do
 
       false ->
         <<
-          start_bin::binary-size(@block_size - start_pos),
+          start_bin::binary-size(@block_size - ^start_pos),
           rest::binary,
         >> = bin
         write_block(file_data, fd, start_block_index, start_pos, start_bin)
@@ -208,8 +208,8 @@ defmodule Trinity.SimFile do
     end
 
     <<
-      prefix::binary-size(pos),
-      _::binary-size(byte_size(bin)),
+      prefix::binary-size(^pos),
+      _::binary-size(byte_size(^bin)),
       suffix::binary,
     >> = existing_data