diff --git a/src/validation.cpp b/src/validation.cpp
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -3098,6 +3098,9 @@
         // BLOCK_FAILED_CHILD status in future iterations, or, if it's the last
         // one, call InvalidChainFound on it.
         to_mark_failed_or_parked = invalid_walk_tip;
+
+        // Block index must always be in a good state before we unlock cs_main.
+        CheckBlockIndex(config.GetChainParams().GetConsensus());
     }
 
     {
@@ -3133,6 +3136,9 @@
         if (invalidate) {
             InvalidChainFound(to_mark_failed_or_parked);
         }
+
+        // Block index must always be in a good state before we unlock cs_main.
+        CheckBlockIndex(config.GetChainParams().GetConsensus());
     }
 
     // Only notify about a new block tip if the active chain was modified.