diff --git a/Library/Homebrew/tap.rb b/Library/Homebrew/tap.rb
index 395fce2b59..3f0760e43f 100644
--- a/Library/Homebrew/tap.rb
+++ b/Library/Homebrew/tap.rb
@@ -590,17 +590,18 @@ class Tap
     end
     return unless remote
 
+    current_upstream_head = git_repository.origin_branch_name
+    return if current_upstream_head.present? && requested_remote.blank? && git_repository.origin_has_branch?(current_upstream_head)
+
     args = %w[fetch]
     args << "--quiet" if quiet
     args << "origin"
     args << "+refs/heads/*:refs/remotes/origin/*"
     safe_system "git", "-C", path, *args
-
-    current_upstream_head = T.must(git_repository.origin_branch_name)
-    return if requested_remote.blank? && git_repository.origin_has_branch?(current_upstream_head)
-
     git_repository.set_head_origin_auto
 
+    current_upstream_head = git_repository.origin_branch_name if current_upstream_head.nil?
+
     new_upstream_head = T.must(git_repository.origin_branch_name)
     return if new_upstream_head == current_upstream_head