diff --git a/acme4j-client/src/main/java/org/shredzone/acme4j/challenge/OutOfBand01Challenge.java b/acme4j-client/src/main/java/org/shredzone/acme4j/challenge/OutOfBand01Challenge.java
index 39640517..498c16fd 100644
--- a/acme4j-client/src/main/java/org/shredzone/acme4j/challenge/OutOfBand01Challenge.java
+++ b/acme4j-client/src/main/java/org/shredzone/acme4j/challenge/OutOfBand01Challenge.java
@@ -19,7 +19,10 @@ import org.shredzone.acme4j.Session;
 
 /**
  * Implements the {@value TYPE} challenge.
+ *
+ * @deprecated This challenge has been removed from the ACMEv2 specs.
  */
+@Deprecated
 public class OutOfBand01Challenge extends Challenge {
     private static final long serialVersionUID = -7459595198486630582L;
 
diff --git a/acme4j-client/src/test/java/org/shredzone/acme4j/challenge/OutOfBandChallengeTest.java b/acme4j-client/src/test/java/org/shredzone/acme4j/challenge/OutOfBandChallengeTest.java
index d4604b66..218df02c 100644
--- a/acme4j-client/src/test/java/org/shredzone/acme4j/challenge/OutOfBandChallengeTest.java
+++ b/acme4j-client/src/test/java/org/shredzone/acme4j/challenge/OutOfBandChallengeTest.java
@@ -43,6 +43,7 @@ public class OutOfBandChallengeTest {
      * Test that {@link OutOfBand01Challenge} is returning the validation URL.
      */
     @Test
+    @SuppressWarnings("deprecation")
     public void testHttpChallenge() throws IOException {
         OutOfBand01Challenge challenge = new OutOfBand01Challenge(session);
         challenge.unmarshall(getJsonAsObject("oobChallenge"));
diff --git a/src/site/markdown/challenge/oob-01.md b/src/site/markdown/challenge/oob-01.md
index 5a83a6ac..2a8cb490 100644
--- a/src/site/markdown/challenge/oob-01.md
+++ b/src/site/markdown/challenge/oob-01.md
@@ -1,5 +1,7 @@
 # oob-01 Challenge
 
+> **NOTE:** `oob-01` challenge has been removed in ACMEv2.
+
 The `oob-01` challenge is an "out of band" challenge that is used when there is no automatic way of validating ownership of a domain. The client is instead required to perform actions outside of the ACME protocol.
 
 `OutOfBand01Challenge` implements this challenge. Its `getValidationUrl()` method returns a URL that refers to a web page with further instructions about the actions to be taken.