diff --git a/lib/minisign/public_key.rb b/lib/minisign/public_key.rb
index 9fe9550..afa51d7 100644
--- a/lib/minisign/public_key.rb
+++ b/lib/minisign/public_key.rb
@@ -41,6 +41,11 @@ def verify(sig, message)
       "Signature and comment signature verified\nTrusted comment: #{sig.trusted_comment}"
     end
 
+    def to_s
+      data = Base64.strict_encode64("Ed#{@decoded[2..9]}#{@public_key}")
+      "untrusted comment: minisign public key #{key_id}\n#{data}\n"
+    end
+
     private
 
     def ensure_matching_key_ids(key_id1, key_id2)
diff --git a/spec/minisign_spec.rb b/spec/minisign/public_key_spec.rb
similarity index 93%
rename from spec/minisign_spec.rb
rename to spec/minisign/public_key_spec.rb
index 2b029ea..1bda9ef 100644
--- a/spec/minisign_spec.rb
+++ b/spec/minisign/public_key_spec.rb
@@ -27,4 +27,7 @@
       @pk.verify(@signature, @message)
     end.to raise_error("Signature key id is 4CB7A94FABA329A6\nbut the key id in the public key is F15F69C58B18A08")
   end
+  it 'can be written to a file' do
+    expect(@pk.to_s).to eq(File.read('test/minisign.pub'))
+  end
 end