diff --git a/src/index.js b/src/index.js
index b7befa5..91660df 100644
--- a/src/index.js
+++ b/src/index.js
@@ -91,6 +91,7 @@ export { split } from "./split/split"
 export { startsWith } from "./starts-with/starts-with"
 export { endsWith } from "./ends-with/ends-with"
 export { toLower } from "./to-lower/to-lower"
+export { toUpper } from "./to-upper/to-upper"
 export { trim } from "./trim/trim"
 export { contains } from "./contains/contains"
 export { join } from "./join/join"
diff --git a/src/to-lower/to-lower.js b/src/to-lower/to-lower.js
index 89f35b7..51ab18c 100644
--- a/src/to-lower/to-lower.js
+++ b/src/to-lower/to-lower.js
@@ -12,6 +12,4 @@
  * toLower("Lorem Ipsum")
  * // "lorem ipsum"
  */
-const toLower = source => "".toLowerCase.call(source)
-
-export { toLower }
+export const toLower = source => "".toLowerCase.call(source)
diff --git a/src/to-lower/to-lower.test.js b/src/to-lower/to-lower.test.js
index 1775dbc..9b026fd 100644
--- a/src/to-lower/to-lower.test.js
+++ b/src/to-lower/to-lower.test.js
@@ -1,14 +1,10 @@
 import test from "tape"
-import { toLower } from ".."
+import { toLower } from "./to-lower"
 
 test("toLower", t => {
   const source = "Lorem Opsum"
 
-  t.equals(
-    toLower(source),
-    "lorem opsum",
-    "Convert uppercase chars into lowercase"
-  )
+  t.equals(toLower(source), "lorem opsum", "Convert chars into lowercase")
 
   t.end()
 })
diff --git a/src/to-upper/to-upper.js b/src/to-upper/to-upper.js
new file mode 100644
index 0000000..bd22615
--- /dev/null
+++ b/src/to-upper/to-upper.js
@@ -0,0 +1,15 @@
+/**
+ * Convert string to upper case
+ *
+ * @tag String
+ * @signature (source: string): string
+ *
+ * @param {string} source Source string
+ *
+ * @return {string}
+ *
+ * @example
+ * toUpper("Lorem Ipsum")
+ * // "LOREM IPSUM"
+ */
+export const toUpper = source => "".toUpperCase.call(source)
diff --git a/src/to-upper/to-upper.test.js b/src/to-upper/to-upper.test.js
new file mode 100644
index 0000000..7c0eb0d
--- /dev/null
+++ b/src/to-upper/to-upper.test.js
@@ -0,0 +1,10 @@
+import test from "tape"
+import { toUpper } from "./to-upper"
+
+test("toUpper", t => {
+  const source = "Lorem Opsum"
+
+  t.equals(toUpper(source), "LOREM OPSUM", "Convert chars into uppercase")
+
+  t.end()
+})