diff --git a/Library/Homebrew/download_strategy.rb b/Library/Homebrew/download_strategy.rb
index ea8a21162e..7c08865607 100644
--- a/Library/Homebrew/download_strategy.rb
+++ b/Library/Homebrew/download_strategy.rb
@@ -1078,17 +1078,17 @@ class GitHubGitDownloadStrategy < GitDownloadStrategy
 
   sig { returns(String) }
   def default_refspec
-    default_branch.yield_self do |branch|
-      if branch
-        "+refs/heads/#{branch}:refs/remotes/origin/#{branch}"
-      else
-        super
-      end
+    if default_branch
+      "+refs/heads/#{default_branch}:refs/remotes/origin/#{default_branch}"
+    else
+      super
     end
   end
 
   sig { returns(String) }
   def default_branch
+    return @default_branch if defined?(@default_branch)
+
     command! "git",
              args:  ["remote", "set-head", "origin", "--auto"],
              chdir: cached_location
@@ -1097,7 +1097,7 @@ class GitHubGitDownloadStrategy < GitDownloadStrategy
                       args:  ["symbolic-ref", "refs/remotes/origin/HEAD"],
                       chdir: cached_location
 
-    result.stdout[%r{^refs/remotes/origin/(.*)$}, 1]
+    @default_branch = result.stdout[%r{^refs/remotes/origin/(.*)$}, 1]
   end
 end