1 files changed, 6 insertions, 0 deletions
diff --git a/src/build.cc b/src/build.cc
index 701fa92..2910385 100644
--- a/src/build.cc
+++ b/src/build.cc
@@ -418,6 +418,12 @@ Edge* Plan::FindWork() {
 void Plan::ScheduleWork(Edge* edge) {
   Pool* pool = edge->pool();
   if (pool->ShouldDelayEdge()) {
+    // The graph is not completely clean. Some Nodes have duplicate Out edges.
+    // We need to explicitly ignore these here, otherwise their work will get
+    // scheduled twice (see https://github.com/martine/ninja/pull/519)
+    if (ready_.count(edge)) {
+      return;
+    }
     pool->DelayEdge(edge);
     pool->RetrieveReadyEdges(&ready_);
   } else {