diff --git a/modules/juce_core/threads/juce_ThreadPool.cpp b/modules/juce_core/threads/juce_ThreadPool.cpp
index ea8ac60d82..db9cb8db0e 100644
--- a/modules/juce_core/threads/juce_ThreadPool.cpp
+++ b/modules/juce_core/threads/juce_ThreadPool.cpp
@@ -176,6 +176,7 @@ void ThreadPool::addJob (std::function<void()> jobToRun)
 
 int ThreadPool::getNumJobs() const noexcept
 {
+    const ScopedLock sl (lock);
     return jobs.size();
 }