diff --git a/lib/simplecov/source_file.rb b/lib/simplecov/source_file.rb
index c68dfd2d..39bb0447 100644
--- a/lib/simplecov/source_file.rb
+++ b/lib/simplecov/source_file.rb
@@ -268,9 +268,9 @@ def build_branches_report
     #
     def build_branches
       coverage_branch_data = coverage_data.fetch("branches", {})
-      branches = coverage_branch_data.flat_map do |condition, coverage_branches|
+      branches = coverage_branch_data&.flat_map do |condition, coverage_branches|
         build_branches_from(condition, coverage_branches)
-      end
+      end || []
 
       process_skipped_branches(branches)
     end