diff --git a/README.md b/README.md
index 1e2b9ce..43826a3 100644
--- a/README.md
+++ b/README.md
@@ -1,4 +1,4 @@
-# Salvium Zero v0.6.3
+# Salvium Zero v0.6.4
 
 Copyright (c) 2023-2024, Salvium
 Portions Copyright (c) 2014-2023, The Monero Project
@@ -172,7 +172,7 @@ invokes cmake commands as needed.
 
     ```bash
     cd salvium
-    git checkout v0.6.3
+    git checkout v0.6.4
     make
     ```
 
@@ -251,7 +251,7 @@ Tested on a Raspberry Pi Zero with a clean install of minimal Raspbian Stretch (
     ```bash
     git clone https://github.com/salvium/salvium
     cd salvium
-    git checkout v0.6.3
+    git checkout v0.6.4
     ```
 
 * Build:
@@ -370,10 +370,10 @@ application.
     cd salvium
     ```
 
-* If you would like a specific [version/tag](https://github.com/salvium/salvium/tags), do a git checkout for that version. eg. 'v0.6.3'. If you don't care about the version and just want binaries from master, skip this step:
+* If you would like a specific [version/tag](https://github.com/salvium/salvium/tags), do a git checkout for that version. eg. 'v0.6.4'. If you don't care about the version and just want binaries from master, skip this step:
 
     ```bash
-    git checkout v0.6.3
+    git checkout v0.6.4
     ```
 
 * If you are on a 64-bit system, run:
diff --git a/src/blocks/checkpoints.dat b/src/blocks/checkpoints.dat
index cb415cb..20cb921 100644
Binary files a/src/blocks/checkpoints.dat and b/src/blocks/checkpoints.dat differ
diff --git a/src/checkpoints/checkpoints.cpp b/src/checkpoints/checkpoints.cpp
index 5ded649..9c53419 100644
--- a/src/checkpoints/checkpoints.cpp
+++ b/src/checkpoints/checkpoints.cpp
@@ -204,6 +204,7 @@ namespace cryptonote
       ADD_CHECKPOINT2(180,   "e20bc8ac6aabb6b0792f23a29ce42a577c6a57d177a8ac1a51b68fb6de508045", "0x262b40");
       ADD_CHECKPOINT2(190,   "f69fdad7a15471b63a82668b618ee5b2a384291269d944b11974a723c1604124", "0x2856a3");
       ADD_CHECKPOINT2(200,   "eba53fa7006dfcdc837a56c0bc8f0e1883cf34861c26934d680252a6878a3f5d", "0x2aa022");
+      ADD_CHECKPOINT2(90000, "e125b5c1b26521f98e29df6ec88f041c176a2c0a3fcacd5bd0ad2278e9b02fd2", "0xc99801f937888"); // 3546475285149832
     }
     return true;
   }
diff --git a/src/cryptonote_core/blockchain.cpp b/src/cryptonote_core/blockchain.cpp
index 0aaa1b8..ab561e1 100644
--- a/src/cryptonote_core/blockchain.cpp
+++ b/src/cryptonote_core/blockchain.cpp
@@ -1034,13 +1034,27 @@ size_t Blockchain::recalculate_difficulties(boost::optional<uint64_t> start_heig
   LOG_PRINT_L3("Blockchain::" << __func__);
   CRITICAL_REGION_LOCAL(m_blockchain_lock);
 
-  const uint64_t start_height = start_height_opt ? *start_height_opt : check_difficulty_checkpoints().second;
+  //uint64_t start_height = start_height_opt ? *start_height_opt : check_difficulty_checkpoints().second;
+  uint8_t version = get_current_hard_fork_version();
+  uint64_t start_height = 0;
+  if (start_height_opt) {
+    start_height = *start_height_opt;
+  } else {
+    bool found = false;
+    for (size_t i=0; i<num_mainnet_hard_forks; ++i) {
+      if (version == mainnet_hard_forks[i].version) {
+        start_height = mainnet_hard_forks[i].height;
+        found = true;
+        break;
+      }
+    }
+    start_height = std::max(start_height, check_difficulty_checkpoints().second);
+  }
   const uint64_t top_height = m_db->height() - 1;
   MGINFO("Recalculating difficulties from height " << start_height << " to height " << top_height);
 
   std::vector<uint64_t> timestamps;
   std::vector<difficulty_type> difficulties;
-  uint8_t version = get_current_hard_fork_version();
   size_t difficulty_blocks_count;
   if (version == 1) {
     difficulty_blocks_count = DIFFICULTY_BLOCKS_COUNT;
@@ -6128,7 +6142,7 @@ void Blockchain::cancel()
 }
 
 #if defined(PER_BLOCK_CHECKPOINT)
-static const char expected_block_hashes_hash[] = "3cb6d33c311e54f2b8439a3e4cc047f6b9b74db9fd92955f1db131a5dfce1edf";
+static const char expected_block_hashes_hash[] = "5065d5361119a526b7a45e9e5bdf1d5be86f80e9eb43b0398bf0e47489c81c6d";
 void Blockchain::load_compiled_in_block_hashes(const GetCheckpointsCallback& get_checkpoints)
 {
   if (get_checkpoints == nullptr || !m_fast_sync)
diff --git a/src/version.cpp.in b/src/version.cpp.in
index ae661bb..ef29705 100644
--- a/src/version.cpp.in
+++ b/src/version.cpp.in
@@ -1,5 +1,5 @@
 #define DEF_SALVIUM_VERSION_TAG "@VERSIONTAG@"
-#define DEF_SALVIUM_VERSION "0.6.3"
+#define DEF_SALVIUM_VERSION "0.6.4"
 #define DEF_MONERO_VERSION_TAG "release"
 #define DEF_MONERO_VERSION "0.18.3.3"
 #define DEF_MONERO_RELEASE_NAME "Zero"