diff --git a/ffwd-client/src/test/java/com/spotify/ffwd/v1/MetricTest.java b/ffwd-client/src/test/java/com/spotify/ffwd/v1/MetricTest.java
index 3c26204..1b4ab70 100644
--- a/ffwd-client/src/test/java/com/spotify/ffwd/v1/MetricTest.java
+++ b/ffwd-client/src/test/java/com/spotify/ffwd/v1/MetricTest.java
@@ -24,13 +24,14 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertNotNull;
 
-
 import com.google.protobuf.ByteString;
 import com.google.protobuf.InvalidProtocolBufferException;
 import com.spotify.ffwd.protocol1.Protocol1;
 import java.nio.ByteBuffer;
 import java.nio.charset.StandardCharsets;
-import java.util.List;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collections;
 import java.util.Map;
 import org.junit.jupiter.api.Test;
 
@@ -105,9 +106,10 @@ public void testSerializeDistributionValue() throws InvalidProtocolBufferExcepti
 
   private Metric createMetric(Value value, long time){
     final long has = 1L;
-    return  new Metric(has, time,KEY,
-        value, HOST, List.of(TAG1,TAG2
-    ), Map.of(KEY,KEYVALUE) );
+    final Map<String, String> attributes = Collections.singletonMap(KEY, KEYVALUE);
+    return new Metric(has, time,KEY,
+        value, HOST, new ArrayList<>(Arrays.asList(TAG1,TAG2)),
+        attributes);
   }
 
   private double extractValue(Metric metric){
diff --git a/opencensus-exporter/src/main/java/com/spotify/ffwd/FfwdMetricsConverter.java b/opencensus-exporter/src/main/java/com/spotify/ffwd/FfwdMetricsConverter.java
index 1084f8a..b98c51b 100644
--- a/opencensus-exporter/src/main/java/com/spotify/ffwd/FfwdMetricsConverter.java
+++ b/opencensus-exporter/src/main/java/com/spotify/ffwd/FfwdMetricsConverter.java
@@ -21,6 +21,7 @@
 package com.spotify.ffwd;
 
 import com.google.common.base.Strings;
+import com.google.common.collect.ImmutableList;
 import io.opencensus.common.Function;
 import io.opencensus.common.Functions;
 import io.opencensus.exporter.metrics.util.MetricExporter;
@@ -37,6 +38,7 @@
 import java.net.UnknownHostException;
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -67,7 +69,8 @@ protected FfwdMetricsConverter(final FastForward client) {
       new Function<Double, List<com.spotify.ffwd.Metric>>() {
         @Override
         public List<com.spotify.ffwd.Metric> apply(Double value) {
-          return List.of(new com.spotify.ffwd.Metric().value(value));
+          return
+              Collections.singletonList(new com.spotify.ffwd.Metric().value(value));
         }
       };
 
@@ -75,7 +78,8 @@ public List<com.spotify.ffwd.Metric> apply(Double value) {
       new Function<Long, List<com.spotify.ffwd.Metric>>() {
         @Override
         public List<com.spotify.ffwd.Metric> apply(Long value) {
-          return List.of(new com.spotify.ffwd.Metric().value(value));
+          return
+              Collections.singletonList(new com.spotify.ffwd.Metric().value(value));
         }
       };
 
@@ -85,7 +89,7 @@ public List<com.spotify.ffwd.Metric> apply(Long value) {
         @Override
         public List<com.spotify.ffwd.Metric> apply(Distribution distribution) {
           //TODO: Big task of support distributions in Heroic.
-          return List.of();
+          return new ArrayList<>(ImmutableList.of());
         }
       };
   private static final Function<Summary, List<com.spotify.ffwd.Metric>> typedValueSummaryFunction =
@@ -97,7 +101,7 @@ public List<com.spotify.ffwd.Metric> apply(Summary summary) {
               summary.getSnapshot().getValueAtPercentiles();
 
           // TODO: Add stat: min/max/average/p75/p99
-          return List.of(
+          return Collections.singletonList(
               new com.spotify.ffwd.Metric().value(snapshot.get(50).getValue())
           );
         }
diff --git a/opencensus-exporter/src/test/java/com/spotify/ffwd/FfwdMetricsConverterTest.java b/opencensus-exporter/src/test/java/com/spotify/ffwd/FfwdMetricsConverterTest.java
index 7a72717..e4af727 100644
--- a/opencensus-exporter/src/test/java/com/spotify/ffwd/FfwdMetricsConverterTest.java
+++ b/opencensus-exporter/src/test/java/com/spotify/ffwd/FfwdMetricsConverterTest.java
@@ -32,6 +32,7 @@
 import io.opencensus.metrics.export.TimeSeries;
 import io.opencensus.metrics.export.Value;
 import java.io.IOException;
+import java.util.Collections;
 import java.util.List;
 import java.util.Map;
 import org.junit.jupiter.api.BeforeEach;
@@ -62,16 +63,16 @@ void counterisSent() throws IOException {
     Mockito.doNothing().when(client).send(metricCaptor.capture());
 
     converter.export(
-        List.of(
+        Collections.singletonList(
             Metric.createWithOneTimeSeries(
                 MetricDescriptor.create(
                     "rps-requests",
                     "requests",
                     "requests",
                     MetricDescriptor.Type.CUMULATIVE_DOUBLE,
-                    List.of(LabelKey.create("status-code", "rpc status code"))),
+                    Collections.singletonList(LabelKey.create("status-code", "rpc status code"))),
                 TimeSeries.createWithOnePoint(
-                    List.of(LabelValue.create("200")),
+                    Collections.singletonList(LabelValue.create("200")),
                     Point.create(Value.doubleValue(10.0), Timestamp.create(1575323125, 0)),
                     Timestamp.create(1575323125, 0)))));
 
@@ -84,8 +85,9 @@ void counterisSent() throws IOException {
 
   @Test
   void createTags() {
-    final List<LabelKey> keys = List.of(LabelKey.create("status-code", "rpc status code"));
-    final List<LabelValue> values = List.of(LabelValue.create("200"));
+    final List<LabelKey> keys =
+        Collections.singletonList(LabelKey.create("status-code", "rpc status code"));
+    final List<LabelValue> values = Collections.singletonList(LabelValue.create("200"));
 
     final Map<String, String> tags = FfwdMetricsConverter.createTags(keys, values);
 
@@ -94,8 +96,9 @@ void createTags() {
 
   @Test
   void createTagsSkipMissingValue() {
-    final List<LabelKey> keys = List.of(LabelKey.create("status-code", "rpc status code"));
-    final List<LabelValue> values = List.of();
+    final List<LabelKey> keys =
+        Collections.singletonList(LabelKey.create("status-code", "rpc status code"));
+    final List<LabelValue> values = Collections.emptyList();
 
     final Map<String, String> tags = FfwdMetricsConverter.createTags(keys, values);
 
diff --git a/pom.xml b/pom.xml
index 6477650..b4fffd7 100644
--- a/pom.xml
+++ b/pom.xml
@@ -38,7 +38,7 @@
 
   <properties>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-    <maven.compiler.release>11</maven.compiler.release>
+    <maven.compiler.release>8</maven.compiler.release>
     <junit-jupiter.version>5.5.2</junit-jupiter.version>
     <opencensus.version>0.24.0</opencensus.version>
     <auto.value.version>1.2</auto.value.version>