diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/TargetPatternValue.java b/src/main/java/com/google/devtools/build/lib/skyframe/TargetPatternValue.java
index 0237af1..c9d5da3 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/TargetPatternValue.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/TargetPatternValue.java
@@ -333,8 +333,8 @@
         Iterable<PathFragment> blacklistedPackagePrefixes) throws InterruptedException {
       ImmutableSet.Builder<PathFragment> excludedPathsBuilder = ImmutableSet.builder();
       excludedPathsBuilder.addAll(getExcludedSubdirectories());
-      excludedPathsBuilder.addAll(getAllBlacklistedSubdirectoriesToExclude(
-          new InterruptibleSupplier.Instance<>(blacklistedPackagePrefixes)));
+      excludedPathsBuilder.addAll(
+          getAllBlacklistedSubdirectoriesToExclude(() -> blacklistedPackagePrefixes));
       return excludedPathsBuilder.build();
     }
 
diff --git a/src/main/java/com/google/devtools/build/skyframe/InterruptibleSupplier.java b/src/main/java/com/google/devtools/build/skyframe/InterruptibleSupplier.java
index 5f4ab55..db5b7ab 100644
--- a/src/main/java/com/google/devtools/build/skyframe/InterruptibleSupplier.java
+++ b/src/main/java/com/google/devtools/build/skyframe/InterruptibleSupplier.java
@@ -13,31 +13,20 @@
 // limitations under the License.
 package com.google.devtools.build.skyframe;
 
+import com.google.common.base.Preconditions;
 import javax.annotation.Nullable;
 
 /** Supplier that may throw {@link InterruptedException} when value is retrieved. */
 public interface InterruptibleSupplier<T> {
   T get() throws InterruptedException;
 
-  class Instance<T> implements InterruptibleSupplier<T> {
-    private final T instance;
-
-    public Instance(T instance) {
-      this.instance = instance;
-    }
-
-    @Override
-    public T get() {
-      return instance;
-    }
-  }
-
-  class Memoize<T> implements InterruptibleSupplier<T> {
-    private final InterruptibleSupplier<T> delegate;
-    private @Nullable T value = null;
+  /** Memoizes the result of {@code delegate} after the first call to {@link #get}. */
+  final class Memoize<T> implements InterruptibleSupplier<T> {
+    private InterruptibleSupplier<T> delegate;
+    @Nullable private volatile T value = null;
 
     private Memoize(InterruptibleSupplier<T> delegate) {
-      this.delegate = delegate;
+      this.delegate = Preconditions.checkNotNull(delegate);
     }
 
     public static <S> InterruptibleSupplier<S> of(InterruptibleSupplier<S> delegate) {
@@ -55,6 +44,7 @@
       synchronized (this) {
         if (value == null) {
           value = delegate.get();
+          delegate = null; // Free up for GC.
         }
       }
       return value;
diff --git a/src/test/java/com/google/devtools/build/skyframe/InterruptibleSupplierTest.java b/src/test/java/com/google/devtools/build/skyframe/InterruptibleSupplierTest.java
new file mode 100644
index 0000000..bcf29fe
--- /dev/null
+++ b/src/test/java/com/google/devtools/build/skyframe/InterruptibleSupplierTest.java
@@ -0,0 +1,69 @@
+// Copyright 2019 The Bazel Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//    http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+package com.google.devtools.build.skyframe;
+
+import static com.google.common.truth.Truth.assertThat;
+
+import com.google.common.testing.GcFinalization;
+import java.lang.ref.WeakReference;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+
+/** Tests for {@link InterruptibleSupplier}. */
+@RunWith(JUnit4.class)
+public final class InterruptibleSupplierTest {
+
+  private int callCount = 0;
+  private String returnVal = "";
+  private CallCounter callCounter = new CallCounter();
+
+  private final class CallCounter {
+    public String call() {
+      ++callCount;
+      return returnVal;
+    }
+  }
+
+  @Test
+  public void memoize_returnsCorrectResult() throws Exception {
+    InterruptibleSupplier<String> supplier = InterruptibleSupplier.Memoize.of(callCounter::call);
+    returnVal = "abc";
+
+    String result = supplier.get();
+
+    assertThat(result).isEqualTo("abc");
+  }
+
+  @Test
+  public void memoize_onlyCallsDelegateOnce() throws Exception {
+    InterruptibleSupplier<String> supplier = InterruptibleSupplier.Memoize.of(callCounter::call);
+
+    supplier.get();
+    supplier.get();
+
+    assertThat(callCount).isEqualTo(1);
+  }
+
+  @Test
+  public void memoize_freesReferenceToDelegeteAfterGet() throws Exception {
+    InterruptibleSupplier<String> supplier = InterruptibleSupplier.Memoize.of(callCounter::call);
+    WeakReference<Object> ref = new WeakReference<>(callCounter);
+    callCounter = null;
+
+    supplier.get();
+
+    GcFinalization.awaitClear(ref);
+  }
+}