diff --git a/build.gradle b/build.gradle
index 901f8a7bda..e1c8766806 100644
--- a/build.gradle
+++ b/build.gradle
@@ -1,6 +1,6 @@
 buildscript {
   ext.versions = [
-      'kotlin': '1.3.50-eap-86',
+      'kotlin': '1.3.50',
       'jmhPlugin': '0.4.8',
       'animalSnifferPlugin': '1.5.0',
       'dokka': '0.9.18',
diff --git a/okio/src/jvmTest/kotlin/okio/BufferCursorKotlinTest.kt b/okio/src/jvmTest/kotlin/okio/BufferCursorKotlinTest.kt
index a73838ed82..86678f5499 100644
--- a/okio/src/jvmTest/kotlin/okio/BufferCursorKotlinTest.kt
+++ b/okio/src/jvmTest/kotlin/okio/BufferCursorKotlinTest.kt
@@ -23,7 +23,6 @@ import org.junit.runner.RunWith
 import org.junit.runners.Parameterized
 import org.junit.runners.Parameterized.Parameter
 import org.junit.runners.Parameterized.Parameters
-import java.util.Arrays
 import kotlin.test.assertEquals
 import kotlin.test.assertFalse
 import kotlin.test.assertNotSame
@@ -98,7 +97,7 @@ class BufferCursorKotlinTest {
 
     buffer.readAndWriteUnsafe().use { cursor ->
       while (cursor.next() != -1) {
-        Arrays.fill(cursor.data!!, cursor.start, cursor.end, 'x'.toByte())
+        cursor.data!!.fill('x'.toByte(), cursor.start, cursor.end)
       }
     }
 
@@ -127,4 +126,4 @@ class BufferCursorKotlinTest {
     cursor.close()
     assertSame(null, cursor.buffer)
   }
-}
\ No newline at end of file
+}
diff --git a/okio/src/jvmTest/kotlin/okio/TestUtil.kt b/okio/src/jvmTest/kotlin/okio/TestUtil.kt
index e87248cbdc..d39ec028b3 100644
--- a/okio/src/jvmTest/kotlin/okio/TestUtil.kt
+++ b/okio/src/jvmTest/kotlin/okio/TestUtil.kt
@@ -103,11 +103,7 @@ object TestUtil {
   }
 
   @JvmStatic
-  fun repeat(c: Char, count: Int): String {
-    val array = CharArray(count)
-    Arrays.fill(array, c)
-    return String(array)
-  }
+  fun repeat(c: Char, count: Int) = c.toString().repeat(count)
 
   @JvmStatic
   fun assertEquivalent(b1: ByteString, b2: ByteString) {
@@ -296,4 +292,4 @@ object TestUtil {
     /* ktlint-enable no-multi-spaces indent */
     return reversed.toShort()
   }
-}
\ No newline at end of file
+}