2 files changed, 2 insertions, 1 deletions
diff --git a/absl/synchronization/mutex.cc b/absl/synchronization/mutex.cc
index df7577b5..3aa5560a 100644
--- a/absl/synchronization/mutex.cc
+++ b/absl/synchronization/mutex.cc
@@ -36,6 +36,7 @@
 #include <algorithm>
 #include <atomic>
 #include <cstddef>
+#include <cstdlib>
 #include <cstring>
 #include <thread>  // NOLINT(build/c++11)
 
diff --git a/absl/synchronization/mutex.h b/absl/synchronization/mutex.h
index 184a585a..2fd077c8 100644
--- a/absl/synchronization/mutex.h
+++ b/absl/synchronization/mutex.h
@@ -513,7 +513,7 @@ class ABSL_LOCKABLE Mutex {
       base_internal::PerThreadSynch* w);  // used for CondVar->Mutex transfer
 
   // Catch the error of writing Mutex when intending MutexLock.
-  Mutex(const volatile Mutex* /*ignored*/) {}  // NOLINT(runtime/explicit)
+  explicit Mutex(const volatile Mutex* /*ignored*/) {}
 
   Mutex(const Mutex&) = delete;
   Mutex& operator=(const Mutex&) = delete;