diff --git a/libc/system_properties/include/system_properties/system_properties.h b/libc/system_properties/include/system_properties/system_properties.h
index fa5e3de..4d84b39 100644
--- a/libc/system_properties/include/system_properties/system_properties.h
+++ b/libc/system_properties/include/system_properties/system_properties.h
@@ -53,7 +53,8 @@
   const char* c_str() { return filename_; }
 
  private:
-  char filename_[1024];
+  // Typically something like "/dev/__properties__/properties_serial".
+  char filename_[128];
 };
 
 class SystemProperties {