diff --git a/libdaggy/src/DAGRunner.cpp b/libdaggy/src/DAGRunner.cpp
index 89a75c8..84dc83f 100644
--- a/libdaggy/src/DAGRunner.cpp
+++ b/libdaggy/src/DAGRunner.cpp
@@ -109,7 +109,9 @@ namespace daggy {
     */
 
     while (n_submitted < MAX_SUBMITS) {
-      auto t                       = dag_.visitNext();
+      auto t = dag_.visitNext();
+      if (!t)
+        continue;
       auto &taskName               = t.value().first;
       taskAttemptCounts_[taskName] = 1;