diff --git a/lib/mri/rubygems/installer.rb b/lib/mri/rubygems/installer.rb
index 4cda09f200be..5d82ce1b0baf 100644
--- a/lib/mri/rubygems/installer.rb
+++ b/lib/mri/rubygems/installer.rb
@@ -223,7 +223,8 @@ def check_executable_overwrite(filename) # :nodoc:
       line = io.gets
       shebang = /^#!.*ruby/
 
-      if load_relative_enabled?
+      # TruffleRuby uses a bash prelude in default launchers
+      if load_relative_enabled? or defined?(::TruffleRuby)
         until line.nil? || line =~ shebang do
           line = io.gets
         end