1 files changed, 8 insertions, 0 deletions
diff --git a/src/main.cpp b/src/main.cpp
index f0aa3022cd..8dd61a3720 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -3232,6 +3232,14 @@ void static CheckBlockIndex()
 
     LOCK(cs_main);
 
+    // During a reindex, we read the genesis block and call CheckBlockIndex before ActivateBestChain,
+    // so we have the genesis block in mapBlockIndex but no active chain.  (A few of the tests when
+    // iterating the block tree require that chainActive has been initialized.)
+    if (chainActive.Height() < 0) {
+        assert(mapBlockIndex.size() <= 1);
+        return;
+    }
+
     // Build forward-pointing map of the entire block tree.
     std::multimap<CBlockIndex*,CBlockIndex*> forward;
     for (BlockMap::iterator it = mapBlockIndex.begin(); it != mapBlockIndex.end(); it++) {