diff --git a/src/graph.cc b/src/graph.cc
index e50e0716..8e6ff697 100644
--- a/src/graph.cc
+++ b/src/graph.cc
@@ -285,8 +285,8 @@ bool DependencyScan::RecomputeOutputDirty(const Edge* edge,
   if (edge->is_phony()) {
     // Phony edges don't write any output.  Outputs are only dirty if
     // there are no inputs or validations and we're missing the output.
-    // If a phony target has inputs or validations, they are used for dirty
-    // calculation instead of this fallback.
+    // If a phony target has inputs or validations, or the output exists,
+    // they are used for dirty calculation instead of this fallback.
     if (edge->inputs_.empty() && edge->validations_.empty() &&
         !output->exists()) {
       explanations_.Record(