diff --git a/Library/Homebrew/tap.rb b/Library/Homebrew/tap.rb
index 741dc9d154d9c..c3fbc5f733da8 100644
--- a/Library/Homebrew/tap.rb
+++ b/Library/Homebrew/tap.rb
@@ -524,10 +524,11 @@ def uninstall(manual: false)
   end
 
   # True if the {#remote} of {Tap} is customized.
+  sig { returns(T::Boolean) }
   def custom_remote?
-    return true unless remote
+    return true unless (remote = self.remote)
 
-    remote.casecmp(default_remote).nonzero?
+    !remote.casecmp(default_remote).zero?
   end
 
   # Path to the directory of all {Formula} files for this {Tap}.
diff --git a/Library/Homebrew/test/tap_spec.rb b/Library/Homebrew/test/tap_spec.rb
index 0fd9fb11d9181..cc7b7f5edaa1f 100644
--- a/Library/Homebrew/test/tap_spec.rb
+++ b/Library/Homebrew/test/tap_spec.rb
@@ -258,6 +258,37 @@ def setup_completion(link:)
     end
   end
 
+  describe "#custom_remote?" do
+    subject(:tap) { described_class.new("Homebrew", "services") }
+
+    let(:remote) { nil }
+
+    before do
+      tap.path.mkpath
+      system "git", "-C", tap.path, "init"
+      system "git", "-C", tap.path, "remote", "add", "origin", remote if remote
+    end
+
+    context "if no remote is available" do
+      it "returns true" do
+        expect(tap.remote).to be_nil
+        expect(tap.custom_remote?).to be true
+      end
+    end
+
+    context "when using the default remote" do
+      let(:remote) { "https://github.com/Homebrew/homebrew-services" }
+
+      its(:custom_remote?) { is_expected.to be false }
+    end
+
+    context "when using a non-default remote" do
+      let(:remote) { "git@github.com:Homebrew/homebrew-services" }
+
+      its(:custom_remote?) { is_expected.to be true }
+    end
+  end
+
   specify "Git variant" do
     touch path/"README"
     setup_git_repo