diff --git a/Library/Homebrew/extend/ENV/super.rb b/Library/Homebrew/extend/ENV/super.rb
index 6417269249..2bf6dd861d 100644
--- a/Library/Homebrew/extend/ENV/super.rb
+++ b/Library/Homebrew/extend/ENV/super.rb
@@ -86,6 +86,8 @@ module Superenv
     self["HOMEBREW_LIBRARY_PATHS"] = determine_library_paths
     self["HOMEBREW_DEPENDENCIES"] = determine_dependencies
     self["HOMEBREW_FORMULA_PREFIX"] = @formula.prefix unless @formula.nil?
+    # Prevent the OpenSSL rust crate from building a vendored OpenSSL.
+    # https://github.com/sfackler/rust-openssl/blob/994e5ff8c63557ab2aa85c85cc6956b0b0216ca7/openssl/src/lib.rs#L65
     self["OPENSSL_NO_VENDOR"] = "1"
 
     set_debug_symbols if debug_symbols