diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8d7ddb8..24f2b19 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,7 @@
 ## HEAD (unreleased)
 
+- Fix performance issue when evaluating multiple block combinations (https://github.com/zombocom/dead_end/pull/35)
+
 ## 1.0.0
 
 - Gem name changed from `syntax_search` to `dead_end` (https://github.com/zombocom/syntax_search/pull/30)
diff --git a/lib/dead_end/code_frontier.rb b/lib/dead_end/code_frontier.rb
index e5659d6..1ba6291 100644
--- a/lib/dead_end/code_frontier.rb
+++ b/lib/dead_end/code_frontier.rb
@@ -143,7 +143,7 @@ def self.combination(array)
     # Given that we know our syntax error exists somewhere in our frontier, we want to find
     # the smallest possible set of blocks that contain all the syntax errors
     def detect_invalid_blocks
-      self.class.combination(@frontier).detect do |block_array|
+      self.class.combination(@frontier.select(&:invalid?)).detect do |block_array|
         holds_all_syntax_errors?(block_array)
       end || []
     end
diff --git a/lib/dead_end/internals.rb b/lib/dead_end/internals.rb
index 92afbcc..ddd5023 100644
--- a/lib/dead_end/internals.rb
+++ b/lib/dead_end/internals.rb
@@ -53,8 +53,9 @@ def self.call(source: , filename: , terminal: false, record_dir: nil, timeout: T
       invalid_obj: invalid_type(source),
       io: io
     ).call
-  rescue Timeout::Error
+  rescue Timeout::Error => e
     io.puts "Search timed out DEAD_END_TIMEOUT=#{timeout}, run with DEBUG=1 for more info"
+    io.puts e.backtrace.first(3).join($/)
   end
 
   # Used for counting spaces
diff --git a/spec/fixtures/routes.txt.rb b/spec/fixtures/routes.txt.rb
new file mode 100644
index 0000000..c4c7a16
--- /dev/null
+++ b/spec/fixtures/routes.txt.rb
@@ -0,0 +1,121 @@
+Rails.application.routes.draw do
+  constraints -> { Rails.application.config.non_production } do
+    namespace :foo do
+      resource :bar
+    end
+  end
+  constraints -> { Rails.application.config.non_production } do
+    namespace :bar do
+      resource :baz
+    end
+  end
+  constraints -> { Rails.application.config.non_production } do
+    namespace :bar do
+      resource :baz
+    end
+  end
+  constraints -> { Rails.application.config.non_production } do
+    namespace :bar do
+      resource :baz
+    end
+  end
+  constraints -> { Rails.application.config.non_production } do
+    namespace :bar do
+      resource :baz
+    end
+  end
+  constraints -> { Rails.application.config.non_production } do
+    namespace :bar do
+      resource :baz
+    end
+  end
+  constraints -> { Rails.application.config.non_production } do
+    namespace :bar do
+      resource :baz
+    end
+  end
+  constraints -> { Rails.application.config.non_production } do
+    namespace :bar do
+      resource :baz
+    end
+  end
+  constraints -> { Rails.application.config.non_production } do
+    namespace :bar do
+      resource :baz
+    end
+  end
+  constraints -> { Rails.application.config.non_production } do
+    namespace :bar do
+      resource :baz
+    end
+  end
+  constraints -> { Rails.application.config.non_production } do
+    namespace :bar do
+      resource :baz
+    end
+  end
+  constraints -> { Rails.application.config.non_production } do
+    namespace :bar do
+      resource :baz
+    end
+  end
+  constraints -> { Rails.application.config.non_production } do
+    namespace :bar do
+      resource :baz
+    end
+  end
+  constraints -> { Rails.application.config.non_production } do
+    namespace :bar do
+      resource :baz
+    end
+  end
+  constraints -> { Rails.application.config.non_production } do
+    namespace :bar do
+      resource :baz
+    end
+  end
+  constraints -> { Rails.application.config.non_production } do
+    namespace :bar do
+      resource :baz
+    end
+  end
+  constraints -> { Rails.application.config.non_production } do
+    namespace :bar do
+      resource :baz
+    end
+  end
+  constraints -> { Rails.application.config.non_production } do
+    namespace :bar do
+      resource :baz
+    end
+  end
+  constraints -> { Rails.application.config.non_production } do
+    namespace :bar do
+      resource :baz
+    end
+  end
+  constraints -> { Rails.application.config.non_production } do
+    namespace :bar do
+      resource :baz
+    end
+  end
+  constraints -> { Rails.application.config.non_production } do
+    namespace :bar do
+      resource :baz
+    end
+  end
+  constraints -> { Rails.application.config.non_production } do
+    namespace :bar do
+      resource :baz
+    end
+  end
+
+  namespace :admin do
+    resource :session
+
+  match "/out_of_office(*path)", via: :all, to: redirect { |_params, req|
+    uri = URI(req.path.gsub("out_of_office", "in_office"))
+    uri.query = req.query_string.presence
+    uri.to_s
+  }
+end
diff --git a/spec/perf/perf_spec.rb b/spec/perf/perf_spec.rb
new file mode 100644
index 0000000..ffdc956
--- /dev/null
+++ b/spec/perf/perf_spec.rb
@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+require_relative "../spec_helper.rb"
+require "benchmark"
+
+module DeadEnd
+  RSpec.describe "perf" do
+    it "doesnt timeout" do
+      source = fixtures_dir.join("routes.txt.rb").read
+
+      io = StringIO.new
+      bench = Benchmark.measure do
+        DeadEnd.call(
+          io: io,
+          source: source,
+          filename: "none",
+        )
+      end
+
+      expect(io.string).to include(<<~'EOM'.indent(4))
+           1  Rails.application.routes.draw do
+          107    constraints -> { Rails.application.config.non_production } do
+          111    end
+        ❯ 113    namespace :admin do
+        ❯ 116    match "/out_of_office(*path)", via: :all, to: redirect { |_params, req|
+        ❯ 120    }
+          121  end
+      EOM
+
+      expect(bench.real).to be < 1 # second
+    end
+  end
+end