diff --git a/util-tracking/src/main/scala/sbt/util/Tracked.scala b/util-tracking/src/main/scala/sbt/util/Tracked.scala
index cfc1d089f..c6286a832 100644
--- a/util-tracking/src/main/scala/sbt/util/Tracked.scala
+++ b/util-tracking/src/main/scala/sbt/util/Tracked.scala
@@ -100,7 +100,7 @@ object Tracked {
     val changed = help.changed(store, initial)
     val result = f(changed, initial)
     if (changed) {
-      help.save(store, initial)
+      help.save(store, p())
     }
     result
   }
@@ -178,7 +178,7 @@ object Tracked {
     def save(store: CacheStore, value: I): Unit = {
       Hasher.hash(value) match {
         case Success(keyHash) => store.write[Long](keyHash.toLong)
-        case Failure(e)       => ()
+        case Failure(_)       => ()
       }
     }
 
diff --git a/util-tracking/src/test/scala/sbt/util/TrackedSpec.scala b/util-tracking/src/test/scala/sbt/util/TrackedSpec.scala
index 7db275d1a..8f88cc53a 100644
--- a/util-tracking/src/test/scala/sbt/util/TrackedSpec.scala
+++ b/util-tracking/src/test/scala/sbt/util/TrackedSpec.scala
@@ -1,12 +1,11 @@
 package sbt.util
 
+import org.scalatest.FlatSpec
 import sbt.io.IO
 import sbt.io.syntax._
+import sbt.util.CacheImplicits._
 
-import CacheImplicits._
-
-import sjsonnew.IsoString
-import org.scalatest.FlatSpec
+import scala.concurrent.Promise
 
 class TrackedSpec extends FlatSpec {
   "lastOutput" should "store the last output" in {
@@ -19,14 +18,14 @@ class TrackedSpec extends FlatSpec {
           case (in, None) =>
             assert(in === value)
             in
-          case (in, Some(_)) =>
+          case (_, Some(_)) =>
             fail()
         }(implicitly)(value)
       assert(res0 === value)
 
       val res1 =
         Tracked.lastOutput[Int, Int](store) {
-          case (in, None) =>
+          case (_, None) =>
             fail()
           case (in, Some(read)) =>
             assert(in === otherValue)
@@ -37,7 +36,7 @@ class TrackedSpec extends FlatSpec {
 
       val res2 =
         Tracked.lastOutput[Int, Int](store) {
-          case (in, None) =>
+          case (_, None) =>
             fail()
           case (in, Some(read)) =>
             assert(in === otherValue)
@@ -45,6 +44,8 @@ class TrackedSpec extends FlatSpec {
             read
         }(implicitly)(otherValue)
       assert(res2 === value)
+
+      ()
     }
   }
 
@@ -57,14 +58,14 @@ class TrackedSpec extends FlatSpec {
           case (true, in) =>
             assert(in === input0)
             in
-          case (false, in) =>
+          case (false, _) =>
             fail()
         }(implicitly, implicitly)(input0)
       assert(res0 === input0)
 
       val res1 =
         Tracked.inputChanged[String, String](store) {
-          case (true, in) =>
+          case (true, _) =>
             fail()
           case (false, in) =>
             assert(in === input0)
@@ -72,6 +73,7 @@ class TrackedSpec extends FlatSpec {
         }(implicitly, implicitly)(input0)
       assert(res1 === input0)
 
+      ()
     }
   }
 
@@ -85,7 +87,7 @@ class TrackedSpec extends FlatSpec {
           case (true, in) =>
             assert(in === input0)
             in
-          case (false, in) =>
+          case (false, _) =>
             fail()
         }(implicitly, implicitly)(input0)
       assert(res0 === input0)
@@ -95,39 +97,52 @@ class TrackedSpec extends FlatSpec {
           case (true, in) =>
             assert(in === input1)
             in
-          case (false, in) =>
+          case (false, _) =>
             fail()
         }(implicitly, implicitly)(input1)
       assert(res1 === input1)
 
+      ()
     }
   }
 
   "outputChanged" should "detect that the output has not changed" in {
     withStore { store =>
-      val input0: String = "foo"
-      val p0: () => String = () => input0
+      val beforeCompletion: String = "before-completion"
+      val afterCompletion: String = "after-completion"
+      val sideEffectCompleted = Promise[Unit]
+      val p0: () => String = () => {
+        if (sideEffectCompleted.isCompleted) {
+          afterCompletion
+        } else {
+          sideEffectCompleted.success(())
+          beforeCompletion
+        }
+      }
+      val firstExpectedResult = "first-result"
+      val secondExpectedResult = "second-result"
 
       val res0 =
         Tracked.outputChanged[String, String](store) {
           case (true, in) =>
-            assert(in === input0)
-            in
-          case (false, in) =>
+            assert(in === beforeCompletion)
+            firstExpectedResult
+          case (false, _) =>
             fail()
         }(implicitly)(p0)
-      assert(res0 === input0)
+      assert(res0 === firstExpectedResult)
 
       val res1 =
         Tracked.outputChanged[String, String](store) {
-          case (true, in) =>
+          case (true, _) =>
             fail()
           case (false, in) =>
-            assert(in === input0)
-            in
+            assert(in === afterCompletion)
+            secondExpectedResult
         }(implicitly)(p0)
-      assert(res1 === input0)
+      assert(res1 === secondExpectedResult)
 
+      ()
     }
   }
 
@@ -136,6 +151,8 @@ class TrackedSpec extends FlatSpec {
       Tracked.tstamp(store) { last =>
         assert(last === 0)
       }
+
+      ()
     }
   }
 
@@ -149,6 +166,8 @@ class TrackedSpec extends FlatSpec {
         val difference = System.currentTimeMillis - last
         assert(difference < 1000)
       }
+
+      ()
     }
   }