diff --git a/lib/coverband/adapters/hash_redis_store.rb b/lib/coverband/adapters/hash_redis_store.rb
index d74ab0f0..de39adf7 100644
--- a/lib/coverband/adapters/hash_redis_store.rb
+++ b/lib/coverband/adapters/hash_redis_store.rb
@@ -24,7 +24,7 @@ def initialize(redis, opts = {})
         @redis = redis
         raise 'HashRedisStore requires redis >= 2.6.0' unless supported?
 
-        @ttl = opts[:ttl] || -1
+        @ttl = opts[:ttl]
         @relative_file_converter = opts[:relative_file_converter] || Utils::RelativeFileConverter
       end
 
@@ -71,7 +71,7 @@ def save_report(report)
             updated_time: updated_time
           )
         end
-        json =  {
+        json = {
           ttl: @ttl,
           files_data: files_data
         }.to_json
@@ -129,7 +129,7 @@ def script_input(key:, file:, file_hash:, data:, report_time:, updated_time:)
         coverage_data = data.each_with_index.each_with_object({}) do |(coverage, index), hash|
           hash[index] = coverage if coverage
         end
-        meta =  {
+        meta = {
           first_updated_at: report_time,
           file: file,
           file_hash: file_hash,
@@ -137,9 +137,9 @@ def script_input(key:, file:, file_hash:, data:, report_time:, updated_time:)
           hash_key: key
         }
         meta.merge!(last_updated_at: updated_time) if updated_time
-        { 
+        {
           hash_key: key,
-          meta: meta ,
+          meta: meta,
           coverage: coverage_data
         }
       end
diff --git a/lua/lib/persist-coverage.lua b/lua/lib/persist-coverage.lua
index fa433103..ddb36d07 100644
--- a/lua/lib/persist-coverage.lua
+++ b/lua/lib/persist-coverage.lua
@@ -20,13 +20,10 @@ for _, file_data in ipairs(files_data) do
   hmset(hash_key, file_data.meta)
   redis.call('HSETNX', hash_key, 'first_updated_at', first_updated_at)
   for line, coverage in pairs(file_data.coverage) do
-    if coverage  == '-1' then
-      redis.call("HSET", hash_key, line, coverage)
-    else
-      redis.call("HINCRBY", hash_key, line, coverage)
-    end
+    redis.call("HINCRBY", hash_key, line, coverage)
   end
-  if ttl > -1 then
+  print('ttl = ' .. inspect(ttl))
+  if ttl and ttl ~= cjson.null then
     redis.call("EXPIRE", hash_key, ttl)
   end
 end
diff --git a/lua/test/test-persist-coverage.lua b/lua/test/test-persist-coverage.lua
index c93e0388..1ed031a0 100644
--- a/lua/test/test-persist-coverage.lua
+++ b/lua/test/test-persist-coverage.lua
@@ -28,7 +28,7 @@ describe("persist-coverage", function()
 
     local key = 'hash_key'
     local json = cjson.encode({
-      ttl = -1,
+      ttl = nil,
       files_data = {
         {
           hash_key = "coverband_hash_3_3.coverband_test.runtime../dog.rb.abcd",
@@ -93,7 +93,7 @@ describe("persist-coverage", function()
 
     last_updated_at = "1569453953"
     json = cjson.encode({
-      ttl = -1,
+      ttl = nil,
       files_data = {
         {
           hash_key="coverband_hash_3_3.coverband_test.runtime../dog.rb.abcd",