diff --git a/src/game.rs b/src/game.rs
index 6daf692..f2be14a 100644
--- a/src/game.rs
+++ b/src/game.rs
@@ -1,4 +1,4 @@
-use crate::{Avatar, Dialogue, Ending, Font, Item, Palette, Room, Sprite, TextDirection, Tile, ToBase36, Variable, transform_line_endings, segments_from_string};
+use crate::{Avatar, Dialogue, Ending, Font, Item, Palette, Room, Sprite, TextDirection, Tile, ToBase36, Variable, transform_line_endings, segments_from_string, is_string_numeric};
 use std::error::Error;
 use loe::TransformMode;
 
@@ -221,18 +221,6 @@ impl ToString for Game {
             segments.push(tile.to_string());
         }
 
-        // for some reason the sprites with numeric IDs go first,
-        // then SPR A (avatar), then all the non-numeric IDs
-        fn is_string_numeric(str: String) -> bool {
-            for c in str.chars() {
-                if !c.is_numeric() {
-                    return false;
-                }
-            }
-
-            return true;
-        }
-
         for sprite in &self.sprites {
             if is_string_numeric(sprite.id.to_base36()) {
                 segments.push(sprite.to_string());
diff --git a/src/lib.rs b/src/lib.rs
index 3125425..3b970c7 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -133,6 +133,18 @@ fn segments_from_string(string: String) -> Vec<String> {
     output
 }
 
+// for some reason the sprites with numeric IDs go first,
+// then SPR A (avatar), then all the non-numeric IDs
+fn is_string_numeric(str: String) -> bool {
+    for c in str.chars() {
+        if !c.is_numeric() {
+            return false;
+        }
+    }
+
+    return true;
+}
+
 #[cfg(test)]
 mod test {
     use crate::{from_base36, ToBase36, optional_data_line, mock, segments_from_string};