diff --git a/db/migrate/20121003223358_extract_backtraces.rb b/db/migrate/20121003223358_extract_backtraces.rb
index 7ca3ee6..484149f 100644
--- a/db/migrate/20121003223358_extract_backtraces.rb
+++ b/db/migrate/20121003223358_extract_backtraces.rb
@@ -2,7 +2,7 @@ class ExtractBacktraces < Mongoid::Migration
   def self.up
     say "It could take long time (hours if you have many Notices)"
     Notice.unscoped.all.each do |notice|
-      backtrace = Backtrace.find_or_create(:raw => notice['backtrace'])
+      backtrace = Backtrace.find_or_create(:raw => notice['backtrace'].presence || [])
       notice.backtrace = backtrace
       notice['backtrace'] = nil
       notice.save!
--
libgit2 0.21.2