diff --git a/src/days/day19/mod.rs b/src/days/day19/mod.rs
index 32bf5a4..b85c754 100644
--- a/src/days/day19/mod.rs
+++ b/src/days/day19/mod.rs
@@ -78,15 +78,6 @@ enum Material {
 }
 
 impl Material {
-    pub fn prev(&self) -> Option<Material> {
-        match self {
-            Material::Geode => None,
-            Material::Obsidian => Some(Material::Geode),
-            Material::Clay => Some(Material::Obsidian),
-            Material::Ore => Some(Material::Clay),
-        }
-    }
-
     pub fn next(&self) -> Option<Material> {
         match self {
             Material::Geode => Some(Material::Obsidian),