diff --git a/src/lib.rs b/src/lib.rs
index ab8a015..dea5d47 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -159,14 +159,7 @@ where
 }
 
 fn lowercase(s: &str, f: &mut fmt::Formatter) -> fmt::Result {
-    let mut chars = s.chars().peekable();
-    while let Some(c) = chars.next() {
-        if c == 'Σ' && chars.peek().is_none() {
-            write!(f, "ς")?;
-        } else {
-            write!(f, "{}", c.to_lowercase())?;
-        }
-    }
+    write!(f, "{}", s.to_lowercase())?;
 
     Ok(())
 }
diff --git a/src/snake.rs b/src/snake.rs
index c3c8576..a116e46 100644
--- a/src/snake.rs
+++ b/src/snake.rs
@@ -97,4 +97,10 @@ mod tests {
     t!(test23: "ABC123dEEf456FOO" => "abc123d_e_ef456_foo");
     t!(test24: "abcDEF" => "abc_def");
     t!(test25: "ABcDE" => "a_bc_de");
+    t!(test26: "Σ" => "σ");
+    t!(test27: "ファΣ" => "ファσ");
+    t!(test28: "X̂Σ" => "x̂ς");
+    t!(test29: "XΣ̂" => "xς̂");
+    t!(test30: "XΣフ" => "xςフ");
+    t!(test31: "XΣA" => "xσa");
 }