diff --git a/maven-core/src/main/java/org/apache/maven/project/DefaultProjectBuilder.java b/maven-core/src/main/java/org/apache/maven/project/DefaultProjectBuilder.java
index 0d82a1459365..b3da9a408c46 100644
--- a/maven-core/src/main/java/org/apache/maven/project/DefaultProjectBuilder.java
+++ b/maven-core/src/main/java/org/apache/maven/project/DefaultProjectBuilder.java
@@ -94,7 +94,8 @@
 @Named
 @Singleton
 public class DefaultProjectBuilder implements ProjectBuilder {
-    private static final String BUILDER_PARALLELISM = "maven.projectBuilder.parallelism";
+    public static final String BUILDER_PARALLELISM = "maven.projectBuilder.parallelism";
+    public static final int DEFAULT_BUILDER_PARALLELISM = 4;
 
     private final Logger logger = LoggerFactory.getLogger(getClass());
     private final ModelBuilder modelBuilder;
@@ -221,7 +222,7 @@ class BuildSession {
         }
 
         private int getParallelism(ProjectBuildingRequest request) {
-            int parallelism = Runtime.getRuntime().availableProcessors();
+            int parallelism = DEFAULT_BUILDER_PARALLELISM;
             try {
                 String str = request.getUserProperties().getProperty(BUILDER_PARALLELISM);
                 if (str == null) {
@@ -233,7 +234,7 @@ private int getParallelism(ProjectBuildingRequest request) {
             } catch (Exception e) {
                 // ignore
             }
-            return parallelism;
+            return Math.min(Runtime.getRuntime().availableProcessors(), parallelism);
         }
 
         ProjectBuildingResult build(File pomFile, ModelSource modelSource) throws ProjectBuildingException {