diff --git a/lib/git/lib.rb b/lib/git/lib.rb
index 108b1035..4a685944 100644
--- a/lib/git/lib.rb
+++ b/lib/git/lib.rb
@@ -357,7 +357,11 @@ def change_head_branch(branch_name)
         )
 
         # The branch's full refname
-        (?<refname>[^[[:blank:]]]+)
+        (?:
+          (?<not_a_branch>\(not[[:blank:]]a[[:blank:]]branch\)) |
+          (?:\(HEAD[[:blank:]]detached[[:blank:]]at[[:blank:]](?<detached_ref>[^\)]+)\)) |
+          (?<refname>[^[[:blank:]]]+)
+        )
 
         # Optional symref
         # If this ref is a symbolic reference, this is the ref referenced
@@ -371,13 +375,14 @@ def branches_all
       command_lines('branch', '-a').map do |line|
         match_data = line.match(BRANCH_LINE_REGEXP)
         raise GitExecuteError, 'Unexpected branch line format' unless match_data
+        next nil if match_data[:not_a_branch] || match_data[:detached_ref]
         [
           match_data[:refname],
           !match_data[:current].nil?,
           !match_data[:worktree].nil?,
           match_data[:symref]
         ]
-      end
+      end.compact
     end
 
     def worktrees_all
diff --git a/tests/units/test_branch.rb b/tests/units/test_branch.rb
index c7a12aee..08707b63 100644
--- a/tests/units/test_branch.rb
+++ b/tests/units/test_branch.rb
@@ -50,6 +50,26 @@ def setup
     end
   end
 
+  test 'Git::Base#branchs with detached head' do
+    in_temp_dir do
+      git = Git.init('.', initial_branch: 'master')
+      File.write('file1.txt', 'hello world')
+      git.add('file1.txt')
+      git.commit('Initial commit')
+      git.add_tag('v1.0.0')
+      File.write('file2.txt', 'hello world')
+      git.add('file2.txt')
+      git.commit('Second commit')
+
+      # This will put us in a detached head state
+      git.checkout('v1.0.0')
+
+      branches = assert_nothing_raised { git.branches }
+      assert_equal(1, branches.size)
+      assert_equal('master', branches.first.name)
+    end
+  end
+
   def test_branches_local
     bs = @git.branches.local
     assert(bs.size > 4)