diff --git a/java/execution/impl/src/com/intellij/execution/TestClassCollector.java b/java/execution/impl/src/com/intellij/execution/TestClassCollector.java
index b00de4d4ea11..0d281a0e7a26 100644
--- a/java/execution/impl/src/com/intellij/execution/TestClassCollector.java
+++ b/java/execution/impl/src/com/intellij/execution/TestClassCollector.java
@@ -16,6 +16,7 @@
 package com.intellij.execution;
 
 import com.intellij.execution.testframework.TestSearchScope;
+import com.intellij.openapi.application.ReadAction;
 import com.intellij.openapi.diagnostic.Logger;
 import com.intellij.openapi.module.Module;
 import com.intellij.openapi.roots.CompilerModuleExtension;
@@ -51,8 +52,8 @@ public class TestClassCollector {
     Module module = configuration.getConfigurationModule().getModule();
     List<URL> urls = new ArrayList<>();
 
-    PathsList pathsList = (module == null || configuration.getTestSearchScope() == TestSearchScope.WHOLE_PROJECT ? OrderEnumerator.orderEntries(configuration.getProject()) : OrderEnumerator.orderEntries(module))
-      .runtimeOnly().recursively().getPathsList(); //include jdk to avoid NoClassDefFoundError for classes inside tools.jar
+    PathsList pathsList = ReadAction.compute(() -> (module == null || configuration.getTestSearchScope() == TestSearchScope.WHOLE_PROJECT ? OrderEnumerator.orderEntries(configuration.getProject()) : OrderEnumerator.orderEntries(module))
+      .runtimeOnly().recursively().getPathsList()); //include jdk to avoid NoClassDefFoundError for classes inside tools.jar
     for (VirtualFile file : pathsList.getVirtualFiles()) {
       try {
         urls.add(VfsUtilCore.virtualToIoFile(file).toURI().toURL());