diff --git a/src/main/java/com/google/devtools/build/lib/sandbox/AbstractSandboxSpawnRunner.java b/src/main/java/com/google/devtools/build/lib/sandbox/AbstractSandboxSpawnRunner.java
index cb6fcfed42000f..6b69f1edc367e3 100644
--- a/src/main/java/com/google/devtools/build/lib/sandbox/AbstractSandboxSpawnRunner.java
+++ b/src/main/java/com/google/devtools/build/lib/sandbox/AbstractSandboxSpawnRunner.java
@@ -372,7 +372,7 @@ protected ImmutableSet<Path> getWritableDirs(Path sandboxExecRoot, Map<String, S
     // On Windows, sandboxExecRoot is actually the main execroot. We will specify
     // exactly which output path is writable.
     if (OS.getCurrent() != OS.WINDOWS) {
-      writablePaths.add(execRoot);
+      writablePaths.add(sandboxExecRoot);
     }
 
     String testTmpdir = env.get("TEST_TMPDIR");