diff --git a/.gitignore b/.gitignore
index 5d434881df..bc83b6a1e5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -82,6 +82,8 @@ lcov*.info
 /goruby
 /id.[ch]
 /largefile.h
+/lcov-c-out
+/lcov-rb-out
 /lcov-out
 /lex.c
 /libruby*.*
diff --git a/Makefile.in b/Makefile.in
index 574b4891b6..b977e8c6fd 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -500,7 +500,6 @@ gcov:
 
 lcov:
 	$(Q) $(BASERUBY) $(srcdir)/tool/run-lcov.rb
-	$(Q) genhtml --ignore-errors source lcov-c-all.info -o lcov-out
 
 update-doclie:
 	$(Q) $(srcdir)/tool/git-refresh -C $(srcdir)/coverage $(Q1:0=-q) \
diff --git a/tool/run-lcov.rb b/tool/run-lcov.rb
index 384d4a9e70..daf52e69b3 100644
--- a/tool/run-lcov.rb
+++ b/tool/run-lcov.rb
@@ -24,18 +24,59 @@ def run_lcov(dir, info)
   system("lcov", "-c", "-d", dir, "--rc", "lcov_branch_coverage=1", "-o", info)
 end
 
+def gen_rb_lcov(file)
+  res = Marshal.load(File.binread(file))
+
+  open("lcov-rb-all.info", "w") do |f|
+    f.puts "TN:" # no test name
+    base_dir = File.dirname(__dir__)
+    res.each do |path, cov|
+      next unless path.start_with?(base_dir)
+      next if path.start_with?(File.join(base_dir, "test"))
+      f.puts "SF:#{ path }"
+
+      total = covered = 0
+      cov.each_with_index do |count, lineno|
+        next unless count
+        f.puts "DA:#{ lineno + 1 },#{ count }"
+        total += 1
+        covered += 1 if count > 0
+      end
+      f.puts "LF:#{ total }"
+      f.puts "LH:#{ covered }"
+
+      f.puts "end_of_record"
+    end
+  end
+end
+
 gcda_files = Pathname.glob("**/*.gcda")
 ext_gcda_files = gcda_files.select {|f| f.fnmatch("ext/*") }
 rubyspec_temp_gcda_files = gcda_files.select {|f| f.fnmatch("rubyspec_temp/*") }
 
 backup_gcda_files(rubyspec_temp_gcda_files) do
-  backup_gcda_files(ext_gcda_files) do
-    info = "lcov-root.info"
-    run_lcov(".", info)
+  if ext_gcda_files != []
+    backup_gcda_files(ext_gcda_files) do
+      info = "lcov-root.info"
+      run_lcov(".", info)
+    end
   end
   ext_gcda_files.group_by {|f| f.descend.to_a[1] }.each do |key, files|
     info = "lcov-#{ key.to_s.gsub(File::Separator, "-") }.info"
     run_lcov(key.to_s, info)
   end
 end
-system("lcov", *$info_files.flat_map {|f| ["-a", f] }, "-o", "lcov-c-all.info")
+if $info_files != []
+  system("lcov", *$info_files.flat_map {|f| ["-a", f] }, "-o", "lcov-c-all.info")
+  system("genhtml", "--ignore-errors", "source", "lcov-c-all.info", "-o", "lcov-c-out")
+end
+
+if File.readable?("test-coverage.dat")
+  gen_rb_lcov("test-coverage.dat")
+  system("genhtml", "--ignore-errors", "source", "lcov-rb-all.info", "-o", "lcov-rb-out")
+end
+
+if File.readable?("lcov-c-all.info") && File.readable?("lcov-rb-all.info")
+  system("lcov", "-a", "lcov-c-all.info", "-a", "lcov-rb-all.info", "-o", "lcov-all.info") || raise
+  system("genhtml", "--ignore-errors", "source", "lcov-all.info", "-o", "lcov-out")
+end