diff --git a/build.gradle b/build.gradle
index 5a19080..7f1a650 100644
--- a/build.gradle
+++ b/build.gradle
@@ -1,8 +1,8 @@
 group 'com.github.sanity'
-version '1.4.7'
+version '1.4.8'
 
 buildscript {
-    ext.kotlin_version = '1.1.50'
+    ext.kotlin_version = '1.1.60'
     ext.dokka_version = '0.9.9'
 
     repositories {
diff --git a/src/main/kotlin/com/github/sanity/pav/PairAdjacentViolators.kt b/src/main/kotlin/com/github/sanity/pav/PairAdjacentViolators.kt
index 68ecd6f..cd521ec 100644
--- a/src/main/kotlin/com/github/sanity/pav/PairAdjacentViolators.kt
+++ b/src/main/kotlin/com/github/sanity/pav/PairAdjacentViolators.kt
@@ -63,8 +63,11 @@ class PairAdjacentViolators @JvmOverloads constructor(originalPoints: Iterable<P
             return { _ -> isotonicPoints.first().y }
         } else {
             when (strategy) {
-                SPLINE -> return {
-                    MonotoneSpline(isotonicPoints).interpolate(it, extrapolation)
+                SPLINE -> {
+                    val spline = MonotoneSpline(isotonicPoints)
+                    return {
+                        spline.interpolate(it, extrapolation)
+                    }
                 }
             }
         }
@@ -75,9 +78,11 @@ class PairAdjacentViolators @JvmOverloads constructor(originalPoints: Iterable<P
             return { _ -> isotonicPoints.first().x }
         } else {
             when (strategy) {
-                SPLINE -> return {
+                SPLINE -> {
                     val spline = MonotoneSpline(isotonicPoints.map { Point(it.y, it.x) })
-                    spline.interpolate(it, extrapolation)
+                    return {
+                        spline.interpolate(it, extrapolation)
+                    }
                 }
             }
         }