diff --git a/src/main/java/com/google/devtools/build/lib/sandbox/SandboxModule.java b/src/main/java/com/google/devtools/build/lib/sandbox/SandboxModule.java
index 8c8c0df..5de2c6d 100644
--- a/src/main/java/com/google/devtools/build/lib/sandbox/SandboxModule.java
+++ b/src/main/java/com/google/devtools/build/lib/sandbox/SandboxModule.java
@@ -528,6 +528,8 @@
       sandboxBase = null;
     }
 
+    spawnRunners.clear();
+
     env.getEventBus().unregister(this);
     env = null;
   }