diff --git a/platform/platform_mac.mm b/platform/platform_mac.mm
index 8faf8c7dd3..0d93674a0a 100644
--- a/platform/platform_mac.mm
+++ b/platform/platform_mac.mm
@@ -137,7 +137,7 @@ Platform::Platform()
   if (tempDir == nil)
       tempDir = @"/tmp";
   m_tmpDir = tempDir.UTF8String;
-  m_tmpDir += '/';
+  base::AddSlashIfNeeded(m_tmpDir);
 
   m_guiThread = std::make_unique<platform::GuiThread>();