diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4d2b663d..f4c11e57 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -23,6 +23,8 @@
 - cdk-mintd: Updated to use new mint lifecycle methods for improved service management ([thesimplekid]).
 - cdk-integration-tests: Updated test utilities to use new mint lifecycle management ([thesimplekid]).
 
+### Fixed
+- cashu: Fixed CurrencyUnit custom units preserving original case instead of being converted to uppercase ([thesimplekid]).
 
 
 ## [0.11.0](https://github.com/cashubtc/cdk/releases/tag/v0.11.0)
diff --git a/crates/cashu/src/nuts/nut00/mod.rs b/crates/cashu/src/nuts/nut00/mod.rs
index 3996800f..cbcbf061 100644
--- a/crates/cashu/src/nuts/nut00/mod.rs
+++ b/crates/cashu/src/nuts/nut00/mod.rs
@@ -591,14 +591,14 @@ impl CurrencyUnit {
 impl FromStr for CurrencyUnit {
     type Err = Error;
     fn from_str(value: &str) -> Result<Self, Self::Err> {
-        let value = &value.to_uppercase();
-        match value.as_str() {
+        let upper_value = value.to_uppercase();
+        match upper_value.as_str() {
             "SAT" => Ok(Self::Sat),
             "MSAT" => Ok(Self::Msat),
             "USD" => Ok(Self::Usd),
             "EUR" => Ok(Self::Eur),
             "AUTH" => Ok(Self::Auth),
-            c => Ok(Self::Custom(c.to_string())),
+            _ => Ok(Self::Custom(value.to_string())),
         }
     }
 }
@@ -977,4 +977,12 @@ mod tests {
             .unwrap();
         assert_eq!(b.len(), 1);
     }
+
+    #[test]
+    fn custom_unit_ser_der() {
+        let unit = CurrencyUnit::Custom(String::from("test"));
+        let serialized = serde_json::to_string(&unit).unwrap();
+        let deserialized: CurrencyUnit = serde_json::from_str(&serialized).unwrap();
+        assert_eq!(unit, deserialized)
+    }
 }