diff --git a/CHANGELOG.md b/CHANGELOG.md
index c72a4798de..67d0f340c7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 - [#2918](https://github.com/poanetwork/blockscout/pull/2918) - Add tokenID for tokentx API action
 
 ### Fixes
+- [#2915](https://github.com/poanetwork/blockscout/pull/2915) - Speedup of blocks_without_reward_query
 - [#2914](https://github.com/poanetwork/blockscout/pull/2914) - Reduce execution time of stream_unfetched_token_instances query
 - [#2906](https://github.com/poanetwork/blockscout/pull/2906) - fix address sum cache
 - [#2902](https://github.com/poanetwork/blockscout/pull/2902) - Offset in blocks retrieval for average block time
diff --git a/apps/explorer/lib/explorer/chain/block.ex b/apps/explorer/lib/explorer/chain/block.ex
index 32905cf076..83aecafa9f 100644
--- a/apps/explorer/lib/explorer/chain/block.ex
+++ b/apps/explorer/lib/explorer/chain/block.ex
@@ -116,11 +116,23 @@ defmodule Explorer.Chain.Block do
   end
 
   def blocks_without_reward_query do
+    consensus_blocks_query =
+      from(
+        b in __MODULE__,
+        where: b.consensus == true
+      )
+
+    validator_rewards =
+      from(
+        r in Reward,
+        where: r.address_type == ^"validator"
+      )
+
     from(
-      b in __MODULE__,
-      left_join: r in Reward,
+      b in subquery(consensus_blocks_query),
+      left_join: r in subquery(validator_rewards),
       on: [block_hash: b.hash],
-      where: is_nil(r.block_hash) and b.consensus == true
+      where: is_nil(r.block_hash)
     )
   end
 
diff --git a/apps/explorer/priv/repo/migrations/20191208135613_block_rewards_block_hash_partial_index.exs b/apps/explorer/priv/repo/migrations/20191208135613_block_rewards_block_hash_partial_index.exs
new file mode 100644
index 0000000000..0b0fa86a4a
--- /dev/null
+++ b/apps/explorer/priv/repo/migrations/20191208135613_block_rewards_block_hash_partial_index.exs
@@ -0,0 +1,9 @@
+defmodule Explorer.Repo.Migrations.BlockRewardsBlockHashPartialIndex do
+  use Ecto.Migration
+
+  def change do
+    execute(
+      "CREATE INDEX IF NOT EXISTS block_rewards_block_hash_partial_index on block_rewards(block_hash) WHERE address_type='validator';"
+    )
+  end
+end