diff --git a/src/qt/walletframe.cpp b/src/qt/walletframe.cpp
--- a/src/qt/walletframe.cpp
+++ b/src/qt/walletframe.cpp
@@ -8,6 +8,7 @@
 #include "bitcoingui.h"
 #include "walletview.h"
 
+#include <cassert>
 #include <cstdio>
 
 #include <QHBoxLayout>
@@ -71,6 +72,7 @@
 
     WalletView *walletView = mapWalletViews.value(name);
     walletStack->setCurrentWidget(walletView);
+    assert(walletView);
     walletView->updateEncryptionStatus();
     return true;
 }
diff --git a/src/validation.cpp b/src/validation.cpp
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -1708,6 +1708,7 @@
     // further duplicate transactions descending from the known pairs either. If
     // we're on the known chain at height greater than where BIP34 activated, we
     // can save the db accesses needed for the BIP30 check.
+    assert(pindex->pprev);
     CBlockIndex *pindexBIP34height =
         pindex->pprev->GetAncestor(consensusParams.BIP34Height);
     // Only continue to enforce if we're below BIP34 activation height or the
@@ -1891,6 +1892,7 @@
         return false;
     }
 
+    assert(pindex->phashBlock);
     // add this block to the view's block chain
     view.SetBestBlock(pindex->GetBlockHash());
 
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -595,6 +595,10 @@
             continue;
         }
 
+        assert(
+            copyFrom &&
+            "Oldest wallet transaction in range assumed to have been found.");
+
         if (!copyFrom->IsEquivalentTo(*copyTo)) {
             continue;
         }