diff --git a/gradle/dependencies.gradle b/gradle/dependencies.gradle
index 85a1607ff19..d58d067efd9 100644
--- a/gradle/dependencies.gradle
+++ b/gradle/dependencies.gradle
@@ -78,7 +78,7 @@ versions += [
   kafka_10: "1.0.2",
   kafka_11: "1.1.1",
   kafka_20: "2.0.1",
-  kafka_21: "2.1.0",
+  kafka_21: "2.1.1",
   lz4: "1.6.0",
   mavenArtifact: "3.6.1",
   metrics: "2.2.0",
diff --git a/streams/src/main/java/org/apache/kafka/streams/processor/internals/StreamsPartitionAssignor.java b/streams/src/main/java/org/apache/kafka/streams/processor/internals/StreamsPartitionAssignor.java
index 3f3c1233da0..33cce13faeb 100644
--- a/streams/src/main/java/org/apache/kafka/streams/processor/internals/StreamsPartitionAssignor.java
+++ b/streams/src/main/java/org/apache/kafka/streams/processor/internals/StreamsPartitionAssignor.java
@@ -799,7 +799,7 @@ public class StreamsPartitionAssignor implements PartitionAssignor, Configurable
     @Override
     public void onAssignment(final Assignment assignment) {
         final List<TopicPartition> partitions = new ArrayList<>(assignment.partitions());
-        Collections.sort(partitions, PARTITION_COMPARATOR);
+        partitions.sort(PARTITION_COMPARATOR);
 
         final AssignmentInfo info = AssignmentInfo.decode(assignment.userData());
         if (info.errCode() != Error.NONE.code) {
@@ -1009,7 +1009,7 @@ public class StreamsPartitionAssignor implements PartitionAssignor, Configurable
                     if (numPartitions == UNKNOWN) {
                         numPartitions = partitions;
                     } else if (numPartitions != partitions) {
-                        final String[] topics = copartitionGroup.toArray(new String[copartitionGroup.size()]);
+                        final String[] topics = copartitionGroup.toArray(new String[0]);
                         Arrays.sort(topics);
                         throw new org.apache.kafka.streams.errors.TopologyException(String.format("%sTopics not co-partitioned: [%s]", logPrefix, Utils.join(Arrays.asList(topics), ",")));
                     }
diff --git a/tests/docker/Dockerfile b/tests/docker/Dockerfile
index 41a2336c3bc..665dc270405 100644
--- a/tests/docker/Dockerfile
+++ b/tests/docker/Dockerfile
@@ -53,7 +53,6 @@ RUN mkdir -p "/opt/kafka-0.11.0.3" && chmod a+rw /opt/kafka-0.11.0.3 && curl -s
 RUN mkdir -p "/opt/kafka-1.0.2" && chmod a+rw /opt/kafka-1.0.2 && curl -s "$KAFKA_MIRROR/kafka_2.11-1.0.2.tgz" | tar xz --strip-components=1 -C "/opt/kafka-1.0.2"
 RUN mkdir -p "/opt/kafka-1.1.1" && chmod a+rw /opt/kafka-1.1.1 && curl -s "$KAFKA_MIRROR/kafka_2.11-1.1.1.tgz" | tar xz --strip-components=1 -C "/opt/kafka-1.1.1"
 RUN mkdir -p "/opt/kafka-2.0.1" && chmod a+rw /opt/kafka-2.0.1 && curl -s "$KAFKA_MIRROR/kafka_2.12-2.0.1.tgz" | tar xz --strip-components=1 -C "/opt/kafka-2.0.1"
-RUN mkdir -p "/opt/kafka-2.1.0" && chmod a+rw /opt/kafka-2.1.0 && curl -s "$KAFKA_MIRROR/kafka_2.12-2.1.0.tgz" | tar xz --strip-components=1 -C "/opt/kafka-2.1.0"
 RUN mkdir -p "/opt/kafka-2.1.1" && chmod a+rw /opt/kafka-2.1.1 && curl -s "$KAFKA_MIRROR/kafka_2.12-2.1.1.tgz" | tar xz --strip-components=1 -C "/opt/kafka-2.1.1"
 RUN mkdir -p "/opt/kafka-2.2.0" && chmod a+rw /opt/kafka-2.2.0 && curl -s "$KAFKA_MIRROR/kafka_2.12-2.2.0.tgz" | tar xz --strip-components=1 -C "/opt/kafka-2.2.0"
 
@@ -65,7 +64,7 @@ RUN curl -s "$KAFKA_MIRROR/kafka-streams-0.11.0.3-test.jar" -o /opt/kafka-0.11.0
 RUN curl -s "$KAFKA_MIRROR/kafka-streams-1.0.2-test.jar" -o /opt/kafka-1.0.2/libs/kafka-streams-1.0.2-test.jar
 RUN curl -s "$KAFKA_MIRROR/kafka-streams-1.1.1-test.jar" -o /opt/kafka-1.1.1/libs/kafka-streams-1.1.1-test.jar
 RUN curl -s "$KAFKA_MIRROR/kafka-streams-2.0.1-test.jar" -o /opt/kafka-2.0.1/libs/kafka-streams-2.0.1-test.jar
-RUN curl -s "$KAFKA_MIRROR/kafka-streams-2.1.0-test.jar" -o /opt/kafka-2.1.0/libs/kafka-streams-2.1.0-test.jar
+RUN curl -s "$KAFKA_MIRROR/kafka-streams-2.1.1-test.jar" -o /opt/kafka-2.1.1/libs/kafka-streams-2.1.1-test.jar
 
 # The version of Kibosh to use for testing.
 # If you update this, also update vagrant/base.sy
diff --git a/tests/kafkatest/version.py b/tests/kafkatest/version.py
index e5aed5a4d3b..403da03b2f1 100644
--- a/tests/kafkatest/version.py
+++ b/tests/kafkatest/version.py
@@ -119,5 +119,6 @@ V_2_1_0 = KafkaVersion("2.1.0")
 V_2_1_1 = KafkaVersion("2.1.1")
 LATEST_2_1 = V_2_1_1
 
+# 2.2.x versions
 V_2_2_0 = KafkaVersion("2.2.0")
 LATEST_2_2 = V_2_2_0