diff --git a/src/index.ts b/src/index.ts
index b49fdc5..a5036e6 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -16,7 +16,7 @@ export function isUppercase(char = ""): boolean | undefined {
   if (NUMBER_CHAR_RE.test(char)) {
     return undefined;
   }
-  return char.toUpperCase() === char;
+  return char !== char.toLowerCase();
 }
 
 export function splitByCase<T extends string>(str: T): SplitByCase<T>;
diff --git a/test/scule.test.ts b/test/scule.test.ts
index 9981c79..fa79642 100644
--- a/test/scule.test.ts
+++ b/test/scule.test.ts
@@ -30,6 +30,7 @@ describe("splitByCase", () => {
       ["foo", "Bar", "fuzz", "FI", "Zz"],
       ["\\", ".", "-"],
     ],
+    ["new-name-value", ["new-name-value"], ["_"]],
   ])("%s => %s", (input, expected, customSplitters?) => {
     if (customSplitters) {
       expect(splitByCase(input, customSplitters)).toMatchObject(expected);