diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/ArtifactFunction.java b/src/main/java/com/google/devtools/build/lib/skyframe/ArtifactFunction.java
index 8e897fb..ae5231a 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/ArtifactFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/ArtifactFunction.java
@@ -106,7 +106,7 @@
       return null;
     }
     if (!fileValue.exists()) {
-      if (allowedMissingInputs.apply(((RootedPath) fileSkyKey.argument()).getRelativePath())) {
+      if (isAllowedMissingInput(fileSkyKey)) {
         return FileArtifactValue.MISSING_FILE_MARKER;
       } else {
         return missingInputFile(artifact, mandatory, null, env.getListener());
@@ -115,10 +115,17 @@
     try {
       return FileArtifactValue.create(artifact, fileValue);
     } catch (IOException e) {
+      if (isAllowedMissingInput(fileSkyKey)) {
+        return FileArtifactValue.MISSING_FILE_MARKER;
+      }
       throw makeMissingInputFileExn(artifact, mandatory, e, env.getListener());
     }
   }
 
+  private boolean isAllowedMissingInput(SkyKey fileSkyKey) {
+    return allowedMissingInputs.apply(((RootedPath) fileSkyKey.argument()).getRelativePath());
+  }
+
   private static ArtifactValue missingInputFile(Artifact artifact, boolean mandatory,
       Exception failure, EventHandler reporter) throws MissingInputFileException {
     if (!mandatory) {
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/FileStateValue.java b/src/main/java/com/google/devtools/build/lib/skyframe/FileStateValue.java
index 80b43a7..459d1ca 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/FileStateValue.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/FileStateValue.java
@@ -164,11 +164,9 @@
                                         @Nullable TimestampGranularityMonitor tsgm)
         throws InconsistentFilesystemException {
       Preconditions.checkState(stat.isFile(), path);
+
       try {
-        byte[] digest = stat.getDigest();
-        if (digest == null) {
-          digest = path.getFastDigest();
-        }
+        byte[] digest = tryGetDigest(path, stat);
         if (digest == null) {
           long mtime = stat.getLastModifiedTime();
           // Note that TimestampGranularityMonitor#notifyDependenceOnFileTime is a thread-safe
@@ -193,6 +191,19 @@
       }
     }
 
+    @Nullable
+    private static byte[] tryGetDigest(Path path, FileStatusWithDigest stat) throws IOException {
+      try {
+        byte[] digest = stat.getDigest();
+        return digest != null ? digest : path.getFastDigest();
+      } catch (IOException ioe) {
+        if (!path.isReadable()) {
+          return null;
+        }
+        throw ioe;
+      }
+    }
+
     @Override
     public Type getType() {
       return Type.REGULAR_FILE;
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/ArtifactFunctionTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/ArtifactFunctionTest.java
index 5ca1354..aae3254 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/ArtifactFunctionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/ArtifactFunctionTest.java
@@ -21,7 +21,7 @@
 import static org.junit.Assert.assertSame;
 import static org.junit.Assert.fail;
 
-import com.google.common.base.Predicates;
+import com.google.common.base.Predicate;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
@@ -64,6 +64,8 @@
 import org.junit.runners.JUnit4;
 
 import java.io.IOException;
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
 import java.util.Arrays;
 import java.util.HashMap;
 import java.util.HashSet;
@@ -82,6 +84,14 @@
   private static final SkyKey OWNER_KEY = new SkyKey(SkyFunctions.ACTION_LOOKUP, "OWNER");
   private static final ActionLookupKey ALL_OWNER = new SingletonActionLookupKey();
 
+  private PathFragment allowedMissingInput = null;
+  private Predicate<PathFragment> allowedMissingInputsPredicate = new Predicate<PathFragment>() {
+    @Override
+    public boolean apply(PathFragment input) {
+      return input.equals(allowedMissingInput);
+    }
+  };
+
   private Set<Action> actions;
   private boolean fastDigest = false;
   private RecordingDifferencer differencer = new RecordingDifferencer();
@@ -102,8 +112,7 @@
             ImmutableMap.<SkyFunctionName, SkyFunction>builder()
                 .put(SkyFunctions.FILE_STATE, new FileStateFunction(tsgm, externalFilesHelper))
                 .put(SkyFunctions.FILE, new FileFunction(pkgLocator))
-                .put(SkyFunctions.ARTIFACT,
-                    new ArtifactFunction(Predicates.<PathFragment>alwaysFalse()))
+                .put(SkyFunctions.ARTIFACT, new ArtifactFunction(allowedMissingInputsPredicate))
                 .put(SkyFunctions.ACTION_EXECUTION, new SimpleActionExecutionFunction())
                 .put(SkyFunctions.PACKAGE,
                     new PackageFunction(null, null, null, null, null, null, null))
@@ -152,6 +161,52 @@
   }
 
   @Test
+  public void testMissingMandatoryAllowedMissingArtifact() throws Throwable {
+    Artifact input = createSourceArtifact("allowedMissing");
+    allowedMissingInput = input.getRootRelativePath();
+    assertThat(evaluateArtifactValue(input, /*mandatory=*/ true))
+        .isEqualTo(FileArtifactValue.MISSING_FILE_MARKER);
+  }
+
+  @Test
+  public void testUnreadableMandatoryAllowedMissingArtifact() throws Throwable {
+    Artifact input = createSourceArtifact("allowedMissing");
+    file(input.getPath(), "allowedMissing");
+    input.getPath().chmod(0);
+
+    allowedMissingInput = input.getRootRelativePath();
+    assertThat(evaluateArtifactValue(input, /*mandatory=*/ true))
+        .isEqualTo(FileArtifactValue.MISSING_FILE_MARKER);
+  }
+
+  @Test
+  public void testUnreadableInputWithFsWithAvailableDigest() throws Throwable {
+    final byte[] expectedDigest = MessageDigest.getInstance("md5").digest(
+        "someunreadablecontent".getBytes(StandardCharsets.UTF_8));
+    setupRoot(
+        new CustomInMemoryFs() {
+          @Override
+          public byte[] getMD5Digest(Path path) throws IOException {
+            return path.getBaseName().equals("unreadable")
+                ? expectedDigest
+                : super.getMD5Digest(path);
+          }
+        });
+
+    Artifact input = createSourceArtifact("unreadable");
+    Path inputPath = input.getPath();
+    file(inputPath, "dummynotused");
+    inputPath.chmod(0);
+
+    FileArtifactValue value =
+        (FileArtifactValue) evaluateArtifactValue(input, /*mandatory=*/ true);
+
+    FileStatus stat = inputPath.stat();
+    assertThat(value.getSize()).isEqualTo(stat.getSize());
+    assertThat(value.getDigest()).isEqualTo(expectedDigest);
+  }
+
+  @Test
   public void testMissingMandatoryArtifact() throws Throwable {
     Artifact input = createSourceArtifact("input1");
     try {
diff --git a/src/test/java/com/google/devtools/build/lib/skyframe/FileFunctionTest.java b/src/test/java/com/google/devtools/build/lib/skyframe/FileFunctionTest.java
index 873d48d..d9cce8b 100644
--- a/src/test/java/com/google/devtools/build/lib/skyframe/FileFunctionTest.java
+++ b/src/test/java/com/google/devtools/build/lib/skyframe/FileFunctionTest.java
@@ -76,6 +76,8 @@
 import java.io.ObjectInputStream;
 import java.io.ObjectOutputStream;
 import java.io.OutputStream;
+import java.nio.charset.StandardCharsets;
+import java.security.MessageDigest;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
@@ -437,6 +439,44 @@
   }
 
   @Test
+  public void testUnreadableFileWithNoFastDigest() throws Exception {
+    Path p = file("unreadable");
+    p.chmod(0);
+    p.setLastModifiedTime(0L);
+
+    FileValue value = valueForPath(p);
+    assertTrue(value.exists());
+    assertThat(value.getDigest()).isNull();
+
+    p.setLastModifiedTime(10L);
+    assertThat(valueForPath(p)).isNotEqualTo(value);
+
+    p.setLastModifiedTime(0L);
+    assertThat(valueForPath(p)).isEqualTo(value);
+  }
+
+  @Test
+  public void testUnreadableFileWithFastDigest() throws Exception {
+    final byte[] expectedDigest = MessageDigest.getInstance("md5").digest(
+        "blah".getBytes(StandardCharsets.UTF_8));
+
+    createFsAndRoot(
+        new CustomInMemoryFs(manualClock) {
+          @Override
+          protected byte[] getFastDigest(Path path) {
+            return path.getBaseName().equals("unreadable") ? expectedDigest : null;
+          }
+        });
+
+    Path p = file("unreadable");
+    p.chmod(0);
+
+    FileValue value = valueForPath(p);
+    assertThat(value.exists()).isTrue();
+    assertThat(value.getDigest()).isNotNull();
+  }
+
+  @Test
   public void testFileModificationModTime() throws Exception {
     fastMd5 = false;
     Path p = file("file");
@@ -882,6 +922,36 @@
     assertThat(errorInfo.getException().getMessage()).contains("/root/a is no longer a file");
   }
 
+  @Test
+  public void testFilesystemInconsistencies_GetFastDigestAndIsReadableFailure() throws Exception {
+    createFsAndRoot(
+        new CustomInMemoryFs(manualClock) {
+          @Override
+          protected boolean isReadable(Path path) throws IOException {
+            if (path.getBaseName().equals("unreadable")) {
+              throw new IOException("isReadable failed");
+            }
+            return super.isReadable(path);
+          }
+        });
+
+    Path p = file("unreadable");
+    p.chmod(0);
+
+    SequentialBuildDriver driver = makeDriver();
+    SkyKey skyKey = skyKey("unreadable");
+    EvaluationResult<FileValue> result =
+        driver.evaluate(
+            ImmutableList.of(skyKey), false, DEFAULT_THREAD_COUNT, NullEventHandler.INSTANCE);
+    assertTrue(result.hasError());
+    ErrorInfo errorInfo = result.getError(skyKey);
+    assertThat(errorInfo.getException()).isInstanceOf(InconsistentFilesystemException.class);
+    assertThat(errorInfo.getException().getMessage())
+        .contains("encountered error 'isReadable failed'");
+    assertThat(errorInfo.getException().getMessage())
+        .contains("/root/unreadable is no longer a file");
+  }
+
   private void runTestSymlinkCycle(boolean ancestorCycle, boolean startInCycle) throws Exception {
     symlink("a", "b");
     symlink("b", "c");