diff --git a/sandbox/linux/services/credentials.cc b/sandbox/linux/services/credentials.cc
index ca6b59547..4fb5adf88 100644
--- a/sandbox/linux/services/credentials.cc
+++ b/sandbox/linux/services/credentials.cc
@@ -11,6 +11,7 @@
 #include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
+#include <string.h>
 #include <sys/syscall.h>
 #include <sys/types.h>
 #include <sys/wait.h>
@@ -100,7 +101,8 @@ bool ChrootToSafeEmptyDir() {
   // TODO(crbug.com/1247458) Broken in MSan builds after LLVM f1bb30a4956f.
   clone_flags |= CLONE_VM | CLONE_VFORK | CLONE_SETTLS;
 
-  char tls_buf[PTHREAD_STACK_MIN] = {0};
+  char tls_buf[PTHREAD_STACK_MIN];
+  memset(tls_buf, 0, PTHREAD_STACK_MIN * sizeof(char));
   tls = tls_buf;
 #endif