diff --git a/build.gradle b/build.gradle
index 057f8bcb..2cd05148 100644
--- a/build.gradle
+++ b/build.gradle
@@ -77,5 +77,8 @@ subprojects { subproject ->
     tasks.withType(Test).configureEach {
         // Allow EasyMock/CGLIB to use reflection on Java base classes when running on newer JDKs.
         jvmArgs += ["--add-opens", "java.base/java.lang=ALL-UNNAMED"]
+        // org.gradle.jvmargs sizes the daemon, not the forked test JVM, which Gradle otherwise
+        // leaves at 512m. The suite runs against that ceiling, spending most of its GC time there.
+        maxHeapSize = "2g"
     }
 }