diff --git a/src/gn/command_gen.cc b/src/gn/command_gen.cc
index ac94487..f997086 100644
--- a/src/gn/command_gen.cc
+++ b/src/gn/command_gen.cc
@@ -109,12 +109,12 @@
   std::string rule =
       NinjaTargetWriter::RunAndWriteFile(target, resolved, ninja_outputs);
 
-  DCHECK(!rule.empty());
-
   {
     std::lock_guard<std::mutex> lock(write_info->lock);
-    write_info->rules[target->toolchain()].emplace_back(target,
-                                                        std::move(rule));
+    if (!rule.empty()) {
+      write_info->rules[target->toolchain()].emplace_back(target,
+                                                          std::move(rule));
+    }
 
     if (write_info->want_ninja_outputs) {
       write_info->ninja_outputs_map.emplace(target,
diff --git a/src/gn/substitution_writer.cc b/src/gn/substitution_writer.cc
index c9624d7..a1f0254 100644
--- a/src/gn/substitution_writer.cc
+++ b/src/gn/substitution_writer.cc
@@ -384,8 +384,10 @@
   } else if (IsValidRustSubstitution(type)) {
     to_rebase = source.value();
   } else {
-    NOTREACHED() << "Unsupported substitution for this function: "
-                 << type->name;
+    // Do not add NOTREACHED() statement here, as Chromium
+    // nobuild_source_set() templates rely on passing {{cflags}}
+    // substitution expressions (and other C++ specific ones)
+    // to action_foreach(). See https://gn.issues.chromium.org/388100196.
     return std::string();
   }