diff --git a/src/blobstore/implementations/onblocks/datatreestore/impl/LeafTraverser.cpp b/src/blobstore/implementations/onblocks/datatreestore/impl/LeafTraverser.cpp
index fee0f1b1..07d7cd78 100644
--- a/src/blobstore/implementations/onblocks/datatreestore/impl/LeafTraverser.cpp
+++ b/src/blobstore/implementations/onblocks/datatreestore/impl/LeafTraverser.cpp
@@ -96,7 +96,7 @@ namespace blobstore {
                     _traverseExistingSubtree(childNode->get(), leavesPerChild, leavesPerChild, childOffset, true,
                                              [] (uint32_t /*index*/, DataLeafNode* /*leaf*/) {ASSERT(false, "We don't actually traverse any leaves.");},
                                              [] (uint32_t /*index*/) -> Data {ASSERT(false, "We don't actually traverse any leaves.");},
-                                             [] (DataInnerNode* /*node*/) {});
+                                             [] (DataInnerNode* /*node*/) {ASSERT(false, "We don't actually traverse any leaves.");});
                 }
 
                 // Traverse existing children