diff --git a/src/atom/parsers.rs b/src/atom/parsers.rs
index f4686f2..e1954c0 100644
--- a/src/atom/parsers.rs
+++ b/src/atom/parsers.rs
@@ -51,7 +51,9 @@ pub fn version<'a>() -> impl Parser<&'a str, Output = Version> {
     let rev = version_number().preceded_by(tag("-r"));
 
     numbers
-        .and(opt(r#if(|c: &char| c.is_ascii_alphabetic())))
+        .and(opt(r#if(|c: &char| {
+            c.is_ascii_alphabetic() && c.is_ascii_lowercase()
+        })))
         .and(opt(suffixes.preceded_by(tag("_"))))
         .and(opt(rev))
         .map(|(((numbers, letter), suffixes), rev)| Version {
@@ -287,4 +289,11 @@ mod test {
 
         atom().check_finished(it).unwrap();
     }
+
+    #[test]
+    fn test_version_with_uppercase_letter() {
+        let it = InputIter::new("foo/bar-1.0.0V");
+
+        assert!(atom().check_finished(it).is_err());
+    }
 }