electrum: common ancestor is before first changed block

src/bitcoin/electrum/mod.rs

@@ -215,7 +215,8 @@ impl Electrum {
                             None
                         } else {
                             log::info!("Block chain reorganization detected.");
-                            Some(self.bdk_wallet.find_block_at_or_before_height(height))
+                            // We can assume height is positive as genesis block will not have changed.
+                            Some(self.bdk_wallet.find_block_before_height(height))
                         };
                     }
                     Some((_, None)) => continue,

src/bitcoin/electrum/wallet.rs

@@ -295,10 +295,10 @@ impl BdkWallet {
         })
     }
 
-    /// Find the first block in the local chain whose height is less than or equal to this.
-    pub fn find_block_at_or_before_height(&self, height: u32) -> BlockChainTip {
+    /// Find the highest block in the local chain whose height is below this.
+    pub fn find_block_before_height(&self, height: u32) -> BlockChainTip {
         for cp in self.local_chain.iter_checkpoints() {
-            if cp.height() <= height {
+            if cp.height() < height {
                 return BlockChainTip {
                     height: height_i32_from_u32(cp.height()),
                     hash: cp.hash(),