diff --git a/.travis.yml b/.travis.yml
index ba8fe1a3..2e62d361 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,7 +1,6 @@
 language: android
 dist: xenial
 
-
 before_cache:
   - rm -f  $HOME/.gradle/caches/modules-2/modules-2.lock
   - rm -fr $HOME/.gradle/caches/*/plugin-resolution/
diff --git a/kt-extensions/src/main/java/com/mindera/skeletoid/kt/extensions/utils/Collection.kt b/kt-extensions/src/main/java/com/mindera/skeletoid/kt/extensions/utils/Collection.kt
index 1f4e40e8..defdba9c 100644
--- a/kt-extensions/src/main/java/com/mindera/skeletoid/kt/extensions/utils/Collection.kt
+++ b/kt-extensions/src/main/java/com/mindera/skeletoid/kt/extensions/utils/Collection.kt
@@ -1,5 +1,3 @@
 package com.mindera.skeletoid.kt.extensions.utils
 
-fun <T: Any> Collection<T>.nullIfEmpty(): Collection<T>? {
-    return if (isEmpty()) null else this
-}
\ No newline at end of file
+fun <T> Collection<T>.nullIfEmpty() = if (isEmpty()) null else this
\ No newline at end of file
diff --git a/kt-extensions/src/main/java/com/mindera/skeletoid/kt/extensions/utils/ListExt.kt b/kt-extensions/src/main/java/com/mindera/skeletoid/kt/extensions/utils/ListExt.kt
new file mode 100644
index 00000000..3c6e5ea8
--- /dev/null
+++ b/kt-extensions/src/main/java/com/mindera/skeletoid/kt/extensions/utils/ListExt.kt
@@ -0,0 +1,3 @@
+package com.mindera.skeletoid.kt.extensions.utils
+
+fun <T> List<T>.nullIfEmpty() = if (isEmpty()) null else this
\ No newline at end of file
diff --git a/kt-extensions/src/test/java/com/mindera/skeletoid/kt/extensions/utils/CollectionTest.kt b/kt-extensions/src/test/java/com/mindera/skeletoid/kt/extensions/utils/CollectionTest.kt
index fa58a18a..eb5ebe7c 100644
--- a/kt-extensions/src/test/java/com/mindera/skeletoid/kt/extensions/utils/CollectionTest.kt
+++ b/kt-extensions/src/test/java/com/mindera/skeletoid/kt/extensions/utils/CollectionTest.kt
@@ -7,13 +7,13 @@ class CollectionTest {
 
     @Test
     fun `test nullIfEmpty with non empty collection`() {
-        val collection = listOf("One", "Two", "Three")
+        val collection = setOf("One", "Two", "Three")
         Assert.assertNotNull(collection.nullIfEmpty())
     }
 
     @Test
     fun `test nullIfEmpty with empty collection`() {
-        val collection = listOf<String>()
+        val collection = setOf<String>()
         Assert.assertNull(collection.nullIfEmpty())
     }
 }
\ No newline at end of file
diff --git a/kt-extensions/src/test/java/com/mindera/skeletoid/kt/extensions/utils/ListExtTest.kt b/kt-extensions/src/test/java/com/mindera/skeletoid/kt/extensions/utils/ListExtTest.kt
new file mode 100644
index 00000000..aef08513
--- /dev/null
+++ b/kt-extensions/src/test/java/com/mindera/skeletoid/kt/extensions/utils/ListExtTest.kt
@@ -0,0 +1,19 @@
+package com.mindera.skeletoid.kt.extensions.utils
+
+import org.junit.Assert
+import org.junit.Test
+
+class ListExtTest {
+
+    @Test
+    fun `test nullIfEmpty with non empty list`() {
+        val list = listOf("One", "Two", "Three")
+        Assert.assertNotNull(list.nullIfEmpty())
+    }
+
+    @Test
+    fun `test nullIfEmpty with empty list`() {
+        val list = listOf<String>()
+        Assert.assertNull(list.nullIfEmpty())
+    }
+}
\ No newline at end of file