diff --git a/src/test/validation_block_tests.cpp b/src/test/validation_block_tests.cpp
index 00e0a487d..bf16d76b3 100644
--- a/src/test/validation_block_tests.cpp
+++ b/src/test/validation_block_tests.cpp
@@ -165,8 +165,8 @@ BOOST_AUTO_TEST_CASE(processnewblock_signals_ordering)
             // to make sure that eventually we process the full chain - do it here
             for (auto block : blocks) {
                 if (block->vtx.size() == 1) {
-                    bool processed = ProcessNewBlock(Params(), block, true, &ignored, false);
-                    assert(processed);
+                    ProcessNewBlock(Params(), block, true, &ignored, false);
+                    assert(!ignored);
                 }
             }
         });
diff --git a/src/validation.cpp b/src/validation.cpp
index faedb3746..8d7c122db 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -2600,8 +2600,8 @@ bool CChainState::ActivateBestChainStep(CValidationState& state, const CChainPar
 {
     AssertLockHeld(cs_main);
 
-    const CBlockIndex *pindexOldTip = chainActive.Tip();
-    const CBlockIndex *pindexFork = chainActive.FindFork(pindexMostWork);
+    auto pindexOldTip = chainActive.Tip();
+    auto pindexFork = chainActive.FindFork(pindexMostWork);
 
     // Disconnect active blocks which are no longer in the best chain.
     bool fBlocksDisconnected = false;
@@ -2616,6 +2616,23 @@ bool CChainState::ActivateBestChainStep(CValidationState& state, const CChainPar
         fBlocksDisconnected = true;
     }
 
+    // Now mark the blocks we just disconnected as descendants invalid
+    // (note this may not be all descendants).
+    if (fBlocksDisconnected) {
+        auto invalid_walk_tip = pindexOldTip;
+        while (invalid_walk_tip != pindexFork) {
+            auto prev = invalid_walk_tip->pprev;
+            if (prev == pindexFork) {
+                InvalidBlockFound(invalid_walk_tip, state);
+                break;
+            }
+            invalid_walk_tip->nStatus |= BLOCK_FAILED_CHILD;
+            setDirtyBlockIndex.insert(invalid_walk_tip);
+            setBlockIndexCandidates.erase(invalid_walk_tip);
+            invalid_walk_tip = prev;
+        }
+    }
+
     // Build list of new blocks to connect.
     std::vector<CBlockIndex*> vpindexToConnect;
     bool fContinue = true;