diff --git a/lib/rspec/support/ruby_features.rb b/lib/rspec/support/ruby_features.rb
index 0772b1af0..83337e039 100644
--- a/lib/rspec/support/ruby_features.rb
+++ b/lib/rspec/support/ruby_features.rb
@@ -33,7 +33,7 @@ def jruby_version
       end
 
       def rbx?
-        defined?(RUBY_ENGINE) && RUBY_ENGINE == 'rbx'
+        !!defined?(RUBY_ENGINE) && RUBY_ENGINE == 'rbx'
       end
 
       def mri?
@@ -41,7 +41,7 @@ def mri?
       end
 
       def truffleruby?
-        defined?(RUBY_ENGINE) && RUBY_ENGINE == 'truffleruby'
+        !!defined?(RUBY_ENGINE) && RUBY_ENGINE == 'truffleruby'
       end
     end