1 files changed, 4 insertions, 2 deletions
diff --git a/lib/irb.rb b/lib/irb.rb
index 8c3039482e..66149eb455 100644
--- a/lib/irb.rb
+++ b/lib/irb.rb
@@ -930,9 +930,11 @@ module IRB
         when "N"
           @context.irb_name
         when "m"
-          truncate_prompt_main(@context.main.to_s)
+          main_str = @context.main.to_s rescue "!#{$!.class}"
+          truncate_prompt_main(main_str)
         when "M"
-          truncate_prompt_main(@context.main.inspect)
+          main_str = @context.main.inspect rescue "!#{$!.class}"
+          truncate_prompt_main(main_str)
         when "l"
           ltype
         when "i"