diff --git a/BUILD.gn b/BUILD.gn
index 4a2dbf182..954ac3a66 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -494,12 +494,16 @@ if (libyuv_include_tests) {
 }
 
 if (!build_with_chromium) {
-  # Write debug logs to gn_logs.txt.
-  # This is also required for Siso builds.
-  import("//build/gn_logs.gni")
-  lines = [
-            "Generated during 'gn gen' by //BUILD.gn.",
-            "",
-          ] + build_gn_logs
-  write_file("$root_build_dir/gn_logs.txt", lines)
+  # GN evaluates each .gn file once per toolchain, so restricting to default
+  # toolchain will ensure write_file() is called only once.
+  if (current_toolchain == default_toolchain) {
+    # Write debug logs to gn_logs.txt.
+    # This is also required for Siso builds.
+    import("//build/gn_logs.gni")
+    lines = [
+              "Generated during 'gn gen' by //BUILD.gn.",
+              "",
+            ] + build_gn_logs
+    write_file("$root_build_dir/gn_logs.txt", lines)
+  }
 }