diff --git a/infra/recipes/gn.expected/ci_linux.json b/infra/recipes/gn.expected/ci_linux.json
index c973f83..f907deb 100644
--- a/infra/recipes/gn.expected/ci_linux.json
+++ b/infra/recipes/gn.expected/ci_linux.json
@@ -695,6 +695,37 @@
     ]
   },
   {
+    "cmd": [
+      "[START_DIR]/gn/tools/update_reference.sh",
+      "--diff"
+    ],
+    "cwd": "[START_DIR]/gn",
+    "env": {
+      "AR": "[START_DIR]/cipd/bin/llvm-ar",
+      "CC": "[START_DIR]/cipd/bin/clang",
+      "CFLAGS": "--target=x86_64-linux-gnu --sysroot=[START_DIR]/cipd/sysroot",
+      "CXX": "[START_DIR]/cipd/bin/clang++",
+      "LDFLAGS": "--target=x86_64-linux-gnu --sysroot=[START_DIR]/cipd/sysroot -static-libstdc++",
+      "NOBUILD": "1"
+    },
+    "luci_context": {
+      "realm": {
+        "name": "gn:ci"
+      },
+      "resultdb": {
+        "current_invocation": {
+          "name": "invocations/build:8945511751514863184",
+          "update_token": "token"
+        },
+        "hostname": "rdbhost"
+      }
+    },
+    "name": "debug.linux-amd64.Check tools/update_reference.sh",
+    "~followup_annotations": [
+      "@@@STEP_NEST_LEVEL@2@@@"
+    ]
+  },
+  {
     "cmd": [],
     "name": "release"
   },
@@ -831,6 +862,37 @@
     ]
   },
   {
+    "cmd": [
+      "[START_DIR]/gn/tools/update_reference.sh",
+      "--diff"
+    ],
+    "cwd": "[START_DIR]/gn",
+    "env": {
+      "AR": "[START_DIR]/cipd/bin/llvm-ar",
+      "CC": "[START_DIR]/cipd/bin/clang",
+      "CFLAGS": "--target=x86_64-linux-gnu --sysroot=[START_DIR]/cipd/sysroot",
+      "CXX": "[START_DIR]/cipd/bin/clang++",
+      "LDFLAGS": "--target=x86_64-linux-gnu --sysroot=[START_DIR]/cipd/sysroot -static-libstdc++",
+      "NOBUILD": "1"
+    },
+    "luci_context": {
+      "realm": {
+        "name": "gn:ci"
+      },
+      "resultdb": {
+        "current_invocation": {
+          "name": "invocations/build:8945511751514863184",
+          "update_token": "token"
+        },
+        "hostname": "rdbhost"
+      }
+    },
+    "name": "release.linux-amd64.Check tools/update_reference.sh",
+    "~followup_annotations": [
+      "@@@STEP_NEST_LEVEL@2@@@"
+    ]
+  },
+  {
     "cmd": [],
     "name": "release.linux-amd64.upload",
     "~followup_annotations": [
diff --git a/infra/recipes/gn.expected/cipd_exists.json b/infra/recipes/gn.expected/cipd_exists.json
index 3d549d2..5ce1915 100644
--- a/infra/recipes/gn.expected/cipd_exists.json
+++ b/infra/recipes/gn.expected/cipd_exists.json
@@ -695,6 +695,37 @@
     ]
   },
   {
+    "cmd": [
+      "[START_DIR]/gn/tools/update_reference.sh",
+      "--diff"
+    ],
+    "cwd": "[START_DIR]/gn",
+    "env": {
+      "AR": "[START_DIR]/cipd/bin/llvm-ar",
+      "CC": "[START_DIR]/cipd/bin/clang",
+      "CFLAGS": "--target=x86_64-linux-gnu --sysroot=[START_DIR]/cipd/sysroot",
+      "CXX": "[START_DIR]/cipd/bin/clang++",
+      "LDFLAGS": "--target=x86_64-linux-gnu --sysroot=[START_DIR]/cipd/sysroot -static-libstdc++",
+      "NOBUILD": "1"
+    },
+    "luci_context": {
+      "realm": {
+        "name": "infra-internal:ci"
+      },
+      "resultdb": {
+        "current_invocation": {
+          "name": "invocations/build:8945511751514863184",
+          "update_token": "token"
+        },
+        "hostname": "rdbhost"
+      }
+    },
+    "name": "debug.linux-amd64.Check tools/update_reference.sh",
+    "~followup_annotations": [
+      "@@@STEP_NEST_LEVEL@2@@@"
+    ]
+  },
+  {
     "cmd": [],
     "name": "release"
   },
@@ -831,6 +862,37 @@
     ]
   },
   {
+    "cmd": [
+      "[START_DIR]/gn/tools/update_reference.sh",
+      "--diff"
+    ],
+    "cwd": "[START_DIR]/gn",
+    "env": {
+      "AR": "[START_DIR]/cipd/bin/llvm-ar",
+      "CC": "[START_DIR]/cipd/bin/clang",
+      "CFLAGS": "--target=x86_64-linux-gnu --sysroot=[START_DIR]/cipd/sysroot",
+      "CXX": "[START_DIR]/cipd/bin/clang++",
+      "LDFLAGS": "--target=x86_64-linux-gnu --sysroot=[START_DIR]/cipd/sysroot -static-libstdc++",
+      "NOBUILD": "1"
+    },
+    "luci_context": {
+      "realm": {
+        "name": "infra-internal:ci"
+      },
+      "resultdb": {
+        "current_invocation": {
+          "name": "invocations/build:8945511751514863184",
+          "update_token": "token"
+        },
+        "hostname": "rdbhost"
+      }
+    },
+    "name": "release.linux-amd64.Check tools/update_reference.sh",
+    "~followup_annotations": [
+      "@@@STEP_NEST_LEVEL@2@@@"
+    ]
+  },
+  {
     "cmd": [],
     "name": "release.linux-amd64.upload",
     "~followup_annotations": [
diff --git a/infra/recipes/gn.expected/cipd_register.json b/infra/recipes/gn.expected/cipd_register.json
index e9f9e35..5f6178c 100644
--- a/infra/recipes/gn.expected/cipd_register.json
+++ b/infra/recipes/gn.expected/cipd_register.json
@@ -695,6 +695,37 @@
     ]
   },
   {
+    "cmd": [
+      "[START_DIR]/gn/tools/update_reference.sh",
+      "--diff"
+    ],
+    "cwd": "[START_DIR]/gn",
+    "env": {
+      "AR": "[START_DIR]/cipd/bin/llvm-ar",
+      "CC": "[START_DIR]/cipd/bin/clang",
+      "CFLAGS": "--target=x86_64-linux-gnu --sysroot=[START_DIR]/cipd/sysroot",
+      "CXX": "[START_DIR]/cipd/bin/clang++",
+      "LDFLAGS": "--target=x86_64-linux-gnu --sysroot=[START_DIR]/cipd/sysroot -static-libstdc++",
+      "NOBUILD": "1"
+    },
+    "luci_context": {
+      "realm": {
+        "name": "infra-internal:ci"
+      },
+      "resultdb": {
+        "current_invocation": {
+          "name": "invocations/build:8945511751514863184",
+          "update_token": "token"
+        },
+        "hostname": "rdbhost"
+      }
+    },
+    "name": "debug.linux-amd64.Check tools/update_reference.sh",
+    "~followup_annotations": [
+      "@@@STEP_NEST_LEVEL@2@@@"
+    ]
+  },
+  {
     "cmd": [],
     "name": "release"
   },
@@ -831,6 +862,37 @@
     ]
   },
   {
+    "cmd": [
+      "[START_DIR]/gn/tools/update_reference.sh",
+      "--diff"
+    ],
+    "cwd": "[START_DIR]/gn",
+    "env": {
+      "AR": "[START_DIR]/cipd/bin/llvm-ar",
+      "CC": "[START_DIR]/cipd/bin/clang",
+      "CFLAGS": "--target=x86_64-linux-gnu --sysroot=[START_DIR]/cipd/sysroot",
+      "CXX": "[START_DIR]/cipd/bin/clang++",
+      "LDFLAGS": "--target=x86_64-linux-gnu --sysroot=[START_DIR]/cipd/sysroot -static-libstdc++",
+      "NOBUILD": "1"
+    },
+    "luci_context": {
+      "realm": {
+        "name": "infra-internal:ci"
+      },
+      "resultdb": {
+        "current_invocation": {
+          "name": "invocations/build:8945511751514863184",
+          "update_token": "token"
+        },
+        "hostname": "rdbhost"
+      }
+    },
+    "name": "release.linux-amd64.Check tools/update_reference.sh",
+    "~followup_annotations": [
+      "@@@STEP_NEST_LEVEL@2@@@"
+    ]
+  },
+  {
     "cmd": [],
     "name": "release.linux-amd64.upload",
     "~followup_annotations": [
diff --git a/infra/recipes/gn.expected/cq_linux.json b/infra/recipes/gn.expected/cq_linux.json
index 9c42ca7..72f2aef 100644
--- a/infra/recipes/gn.expected/cq_linux.json
+++ b/infra/recipes/gn.expected/cq_linux.json
@@ -746,6 +746,37 @@
     ]
   },
   {
+    "cmd": [
+      "[START_DIR]/gn/tools/update_reference.sh",
+      "--diff"
+    ],
+    "cwd": "[START_DIR]/gn",
+    "env": {
+      "AR": "[START_DIR]/cipd/bin/llvm-ar",
+      "CC": "[START_DIR]/cipd/bin/clang",
+      "CFLAGS": "--target=x86_64-linux-gnu --sysroot=[START_DIR]/cipd/sysroot",
+      "CXX": "[START_DIR]/cipd/bin/clang++",
+      "LDFLAGS": "--target=x86_64-linux-gnu --sysroot=[START_DIR]/cipd/sysroot -static-libstdc++",
+      "NOBUILD": "1"
+    },
+    "luci_context": {
+      "realm": {
+        "name": "gn:try"
+      },
+      "resultdb": {
+        "current_invocation": {
+          "name": "invocations/build:8945511751514863184",
+          "update_token": "token"
+        },
+        "hostname": "rdbhost"
+      }
+    },
+    "name": "debug.linux-amd64.Check tools/update_reference.sh",
+    "~followup_annotations": [
+      "@@@STEP_NEST_LEVEL@2@@@"
+    ]
+  },
+  {
     "cmd": [],
     "name": "release"
   },
@@ -882,6 +913,37 @@
     ]
   },
   {
+    "cmd": [
+      "[START_DIR]/gn/tools/update_reference.sh",
+      "--diff"
+    ],
+    "cwd": "[START_DIR]/gn",
+    "env": {
+      "AR": "[START_DIR]/cipd/bin/llvm-ar",
+      "CC": "[START_DIR]/cipd/bin/clang",
+      "CFLAGS": "--target=x86_64-linux-gnu --sysroot=[START_DIR]/cipd/sysroot",
+      "CXX": "[START_DIR]/cipd/bin/clang++",
+      "LDFLAGS": "--target=x86_64-linux-gnu --sysroot=[START_DIR]/cipd/sysroot -static-libstdc++",
+      "NOBUILD": "1"
+    },
+    "luci_context": {
+      "realm": {
+        "name": "gn:try"
+      },
+      "resultdb": {
+        "current_invocation": {
+          "name": "invocations/build:8945511751514863184",
+          "update_token": "token"
+        },
+        "hostname": "rdbhost"
+      }
+    },
+    "name": "release.linux-amd64.Check tools/update_reference.sh",
+    "~followup_annotations": [
+      "@@@STEP_NEST_LEVEL@2@@@"
+    ]
+  },
+  {
     "cmd": [],
     "name": "release.linux-amd64.upload",
     "~followup_annotations": [
diff --git a/infra/recipes/gn.py b/infra/recipes/gn.py
index 22d7b74..93c9634 100644
--- a/infra/recipes/gn.py
+++ b/infra/recipes/gn.py
@@ -274,6 +274,11 @@
                 with api.context(env={'CLANG_FORMAT': cipd_dir.join('bin', 'clang-format')}):
                   api.step('Check tools/run_formatter.sh',
                            [src_dir.join('tools', 'run_formatter.sh'), '--diff'])
+                # We've already built gn, so tell update_reference not to rebuild it.
+                with api.context(env={'NOBUILD': '1'}):
+                  api.step('Check tools/update_reference.sh',
+                          [src_dir.join('tools', 'update_reference.sh'), '--diff'])
+
             if config['name'] != 'release':
               continue