diff --git a/pom.xml b/pom.xml
index 92d3c97..8fa7de7 100644
--- a/pom.xml
+++ b/pom.xml
@@ -52,12 +52,6 @@
       <version>${mavenResolverVersion}</version>
       <scope>provided</scope>
     </dependency>
-    <dependency>
-      <groupId>com.google.guava</groupId>
-      <artifactId>guava</artifactId>
-      <version>31.0.1-jre</version>
-      <scope>provided</scope>
-    </dependency>
 
     <!-- test dependencies -->
     <dependency>
@@ -79,5 +73,11 @@
       <type>pom</type>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>com.google.guava</groupId>
+      <artifactId>guava</artifactId>
+      <version>31.0.1-jre</version>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 </project>
diff --git a/src/main/java/io/takari/maven/builder/smart/ReactorBuildStats.java b/src/main/java/io/takari/maven/builder/smart/ReactorBuildStats.java
index 1e99ba0..27e28ee 100644
--- a/src/main/java/io/takari/maven/builder/smart/ReactorBuildStats.java
+++ b/src/main/java/io/takari/maven/builder/smart/ReactorBuildStats.java
@@ -1,9 +1,15 @@
 package io.takari.maven.builder.smart;
 
-import com.google.common.collect.ImmutableMap;
 import org.apache.maven.project.MavenProject;
 
-import java.util.*;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicLong;
 import java.util.function.Function;
@@ -32,8 +38,8 @@ class ReactorBuildStats {
 
   private ReactorBuildStats(Map<String, AtomicLong> serviceTimes,
       Map<String, AtomicLong> bottleneckTimes) {
-    this.serviceTimes = ImmutableMap.copyOf(serviceTimes);
-    this.bottleneckTimes = ImmutableMap.copyOf(bottleneckTimes);
+    this.serviceTimes = Collections.unmodifiableMap(serviceTimes);
+    this.bottleneckTimes = Collections.unmodifiableMap(bottleneckTimes);
   }
 
   private static String projectGAV(MavenProject project) {
@@ -41,13 +47,13 @@ private static String projectGAV(MavenProject project) {
   }
 
   public static ReactorBuildStats create(Collection<MavenProject> projects) {
-    ImmutableMap.Builder<String, AtomicLong> serviceTimes = ImmutableMap.builder();
-    ImmutableMap.Builder<String, AtomicLong> bottleneckTimes = ImmutableMap.builder();
+    Map<String, AtomicLong> serviceTimes = new HashMap<>();
+    Map<String, AtomicLong> bottleneckTimes = new HashMap<>();
     projects.stream().map(ReactorBuildStats::projectGAV).forEach(key -> {
       serviceTimes.put(key, new AtomicLong());
       bottleneckTimes.put(key, new AtomicLong());
     });
-    return new ReactorBuildStats(serviceTimes.build(), bottleneckTimes.build());
+    return new ReactorBuildStats(serviceTimes, bottleneckTimes);
   }
 
   public void recordStart() {
diff --git a/src/main/java/io/takari/maven/builder/smart/SmartBuilder.java b/src/main/java/io/takari/maven/builder/smart/SmartBuilder.java
index f26cacd..578e85f 100644
--- a/src/main/java/io/takari/maven/builder/smart/SmartBuilder.java
+++ b/src/main/java/io/takari/maven/builder/smart/SmartBuilder.java
@@ -8,6 +8,7 @@
 import java.util.Set;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
+import java.util.stream.Collectors;
 
 import javax.inject.Inject;
 import javax.inject.Named;
@@ -24,8 +25,6 @@
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
-import com.google.common.base.Joiner;
-
 /**
  * Trivial Maven {@link Builder} implementation. All interesting stuff happens in
  * {@link SmartBuilderImpl} .
@@ -84,7 +83,7 @@ public synchronized void build(final MavenSession session, final ReactorContext
     final int degreeOfConcurrency = session.getRequest().getDegreeOfConcurrency();
 
     if (logger.isDebugEnabled()) {
-      logger.debug("Task segments : {}", Joiner.on(" ").join(taskSegments));
+      logger.debug("Task segments : {}", taskSegments);
       logger.debug("Build maximum degree of concurrency is {}", degreeOfConcurrency);
       logger.debug("Total number of projects is {}", graph.getProjects().count());
     }