diff --git a/spec/bundler/realworld/slow_perf_spec.rb b/spec/bundler/realworld/slow_perf_spec.rb
index 9f11821bf5..467e740cb4 100644
--- a/spec/bundler/realworld/slow_perf_spec.rb
+++ b/spec/bundler/realworld/slow_perf_spec.rb
@@ -11,12 +11,6 @@ RSpec.describe "bundle install with complex dependencies", :realworld => true do
       gem "mongoid", ">= 0.10.2"
     G
 
-    start_time = Time.now
-
-    bundle "lock"
-
-    duration = Time.now - start_time
-
-    expect(duration.to_f).to be < 18 # seconds
+    expect { bundle "lock" }.to take_less_than(18) # seconds
   end
 end
diff --git a/spec/bundler/support/matchers.rb b/spec/bundler/support/matchers.rb
index ce6b216619..8b22e7dbc3 100644
--- a/spec/bundler/support/matchers.rb
+++ b/spec/bundler/support/matchers.rb
@@ -97,6 +97,18 @@ module Spec
       end
     end
 
+    RSpec::Matchers.define :take_less_than do |seconds|
+      match do |actual|
+        start_time = Time.now
+
+        actual.call
+
+        (Time.now - start_time).to_f < seconds
+      end
+
+      supports_block_expectations
+    end
+
     define_compound_matcher :read_as, [exist] do |file_contents|
       diffable