diff --git a/objectivec/GPBAny.pbobjc.h b/objectivec/GPBAny.pbobjc.h
index a9ae0c5304..fbfd4935dc 100644
--- a/objectivec/GPBAny.pbobjc.h
+++ b/objectivec/GPBAny.pbobjc.h
@@ -1,4 +1,5 @@
 // Generated by the protocol buffer compiler.  DO NOT EDIT!
+// NO CHECKED-IN PROTOBUF GENCODE
 // clang-format off
 // source: google/protobuf/any.proto
 
diff --git a/objectivec/GPBAny.pbobjc.m b/objectivec/GPBAny.pbobjc.m
index 2e3b86c2b1..600aafd874 100644
--- a/objectivec/GPBAny.pbobjc.m
+++ b/objectivec/GPBAny.pbobjc.m
@@ -1,4 +1,5 @@
 // Generated by the protocol buffer compiler.  DO NOT EDIT!
+// NO CHECKED-IN PROTOBUF GENCODE
 // clang-format off
 // source: google/protobuf/any.proto
 
diff --git a/objectivec/GPBApi.pbobjc.h b/objectivec/GPBApi.pbobjc.h
index bda3803de7..9348ec3115 100644
--- a/objectivec/GPBApi.pbobjc.h
+++ b/objectivec/GPBApi.pbobjc.h
@@ -1,4 +1,5 @@
 // Generated by the protocol buffer compiler.  DO NOT EDIT!
+// NO CHECKED-IN PROTOBUF GENCODE
 // clang-format off
 // source: google/protobuf/api.proto
 
diff --git a/objectivec/GPBApi.pbobjc.m b/objectivec/GPBApi.pbobjc.m
index 3d1e5b22c4..b37dfe9535 100644
--- a/objectivec/GPBApi.pbobjc.m
+++ b/objectivec/GPBApi.pbobjc.m
@@ -1,4 +1,5 @@
 // Generated by the protocol buffer compiler.  DO NOT EDIT!
+// NO CHECKED-IN PROTOBUF GENCODE
 // clang-format off
 // source: google/protobuf/api.proto
 
diff --git a/objectivec/GPBDuration.pbobjc.h b/objectivec/GPBDuration.pbobjc.h
index c5e27e4e5a..91c124eb88 100644
--- a/objectivec/GPBDuration.pbobjc.h
+++ b/objectivec/GPBDuration.pbobjc.h
@@ -1,4 +1,5 @@
 // Generated by the protocol buffer compiler.  DO NOT EDIT!
+// NO CHECKED-IN PROTOBUF GENCODE
 // clang-format off
 // source: google/protobuf/duration.proto
 
diff --git a/objectivec/GPBDuration.pbobjc.m b/objectivec/GPBDuration.pbobjc.m
index 5919d5ef98..c524cd6df9 100644
--- a/objectivec/GPBDuration.pbobjc.m
+++ b/objectivec/GPBDuration.pbobjc.m
@@ -1,4 +1,5 @@
 // Generated by the protocol buffer compiler.  DO NOT EDIT!
+// NO CHECKED-IN PROTOBUF GENCODE
 // clang-format off
 // source: google/protobuf/duration.proto
 
diff --git a/objectivec/GPBEmpty.pbobjc.h b/objectivec/GPBEmpty.pbobjc.h
index 4c0d1a2cb6..d1233ae0e8 100644
--- a/objectivec/GPBEmpty.pbobjc.h
+++ b/objectivec/GPBEmpty.pbobjc.h
@@ -1,4 +1,5 @@
 // Generated by the protocol buffer compiler.  DO NOT EDIT!
+// NO CHECKED-IN PROTOBUF GENCODE
 // clang-format off
 // source: google/protobuf/empty.proto
 
diff --git a/objectivec/GPBEmpty.pbobjc.m b/objectivec/GPBEmpty.pbobjc.m
index 208718e5d9..e829ec681d 100644
--- a/objectivec/GPBEmpty.pbobjc.m
+++ b/objectivec/GPBEmpty.pbobjc.m
@@ -1,4 +1,5 @@
 // Generated by the protocol buffer compiler.  DO NOT EDIT!
+// NO CHECKED-IN PROTOBUF GENCODE
 // clang-format off
 // source: google/protobuf/empty.proto
 
diff --git a/objectivec/GPBFieldMask.pbobjc.h b/objectivec/GPBFieldMask.pbobjc.h
index a3a6978a99..64447e3f9b 100644
--- a/objectivec/GPBFieldMask.pbobjc.h
+++ b/objectivec/GPBFieldMask.pbobjc.h
@@ -1,4 +1,5 @@
 // Generated by the protocol buffer compiler.  DO NOT EDIT!
+// NO CHECKED-IN PROTOBUF GENCODE
 // clang-format off
 // source: google/protobuf/field_mask.proto
 
diff --git a/objectivec/GPBFieldMask.pbobjc.m b/objectivec/GPBFieldMask.pbobjc.m
index 0f7c890bfa..9db1ed7638 100644
--- a/objectivec/GPBFieldMask.pbobjc.m
+++ b/objectivec/GPBFieldMask.pbobjc.m
@@ -1,4 +1,5 @@
 // Generated by the protocol buffer compiler.  DO NOT EDIT!
+// NO CHECKED-IN PROTOBUF GENCODE
 // clang-format off
 // source: google/protobuf/field_mask.proto
 
diff --git a/objectivec/GPBSourceContext.pbobjc.h b/objectivec/GPBSourceContext.pbobjc.h
index 573cac4a05..60cd04dcbb 100644
--- a/objectivec/GPBSourceContext.pbobjc.h
+++ b/objectivec/GPBSourceContext.pbobjc.h
@@ -1,4 +1,5 @@
 // Generated by the protocol buffer compiler.  DO NOT EDIT!
+// NO CHECKED-IN PROTOBUF GENCODE
 // clang-format off
 // source: google/protobuf/source_context.proto
 
diff --git a/objectivec/GPBSourceContext.pbobjc.m b/objectivec/GPBSourceContext.pbobjc.m
index 42a60ac89b..a3e0539b4b 100644
--- a/objectivec/GPBSourceContext.pbobjc.m
+++ b/objectivec/GPBSourceContext.pbobjc.m
@@ -1,4 +1,5 @@
 // Generated by the protocol buffer compiler.  DO NOT EDIT!
+// NO CHECKED-IN PROTOBUF GENCODE
 // clang-format off
 // source: google/protobuf/source_context.proto
 
diff --git a/objectivec/GPBStruct.pbobjc.h b/objectivec/GPBStruct.pbobjc.h
index 8f2f12c73b..17a5c0774c 100644
--- a/objectivec/GPBStruct.pbobjc.h
+++ b/objectivec/GPBStruct.pbobjc.h
@@ -1,4 +1,5 @@
 // Generated by the protocol buffer compiler.  DO NOT EDIT!
+// NO CHECKED-IN PROTOBUF GENCODE
 // clang-format off
 // source: google/protobuf/struct.proto
 
diff --git a/objectivec/GPBStruct.pbobjc.m b/objectivec/GPBStruct.pbobjc.m
index 21f156fa5e..3ba43b63bc 100644
--- a/objectivec/GPBStruct.pbobjc.m
+++ b/objectivec/GPBStruct.pbobjc.m
@@ -1,4 +1,5 @@
 // Generated by the protocol buffer compiler.  DO NOT EDIT!
+// NO CHECKED-IN PROTOBUF GENCODE
 // clang-format off
 // source: google/protobuf/struct.proto
 
diff --git a/objectivec/GPBTimestamp.pbobjc.h b/objectivec/GPBTimestamp.pbobjc.h
index bdf8ee4186..f2cb405105 100644
--- a/objectivec/GPBTimestamp.pbobjc.h
+++ b/objectivec/GPBTimestamp.pbobjc.h
@@ -1,4 +1,5 @@
 // Generated by the protocol buffer compiler.  DO NOT EDIT!
+// NO CHECKED-IN PROTOBUF GENCODE
 // clang-format off
 // source: google/protobuf/timestamp.proto
 
diff --git a/objectivec/GPBTimestamp.pbobjc.m b/objectivec/GPBTimestamp.pbobjc.m
index 3cad69933e..93e9fbbb41 100644
--- a/objectivec/GPBTimestamp.pbobjc.m
+++ b/objectivec/GPBTimestamp.pbobjc.m
@@ -1,4 +1,5 @@
 // Generated by the protocol buffer compiler.  DO NOT EDIT!
+// NO CHECKED-IN PROTOBUF GENCODE
 // clang-format off
 // source: google/protobuf/timestamp.proto
 
diff --git a/objectivec/GPBType.pbobjc.h b/objectivec/GPBType.pbobjc.h
index 28638fa086..13dcdfb8a4 100644
--- a/objectivec/GPBType.pbobjc.h
+++ b/objectivec/GPBType.pbobjc.h
@@ -1,4 +1,5 @@
 // Generated by the protocol buffer compiler.  DO NOT EDIT!
+// NO CHECKED-IN PROTOBUF GENCODE
 // clang-format off
 // source: google/protobuf/type.proto
 
diff --git a/objectivec/GPBType.pbobjc.m b/objectivec/GPBType.pbobjc.m
index 57896696d5..33360d93ba 100644
--- a/objectivec/GPBType.pbobjc.m
+++ b/objectivec/GPBType.pbobjc.m
@@ -1,4 +1,5 @@
 // Generated by the protocol buffer compiler.  DO NOT EDIT!
+// NO CHECKED-IN PROTOBUF GENCODE
 // clang-format off
 // source: google/protobuf/type.proto
 
diff --git a/objectivec/GPBWrappers.pbobjc.h b/objectivec/GPBWrappers.pbobjc.h
index f03209e56a..b9c46a31e5 100644
--- a/objectivec/GPBWrappers.pbobjc.h
+++ b/objectivec/GPBWrappers.pbobjc.h
@@ -1,4 +1,5 @@
 // Generated by the protocol buffer compiler.  DO NOT EDIT!
+// NO CHECKED-IN PROTOBUF GENCODE
 // clang-format off
 // source: google/protobuf/wrappers.proto
 
diff --git a/objectivec/GPBWrappers.pbobjc.m b/objectivec/GPBWrappers.pbobjc.m
index bf5a8e190f..cae024e4bf 100644
--- a/objectivec/GPBWrappers.pbobjc.m
+++ b/objectivec/GPBWrappers.pbobjc.m
@@ -1,4 +1,5 @@
 // Generated by the protocol buffer compiler.  DO NOT EDIT!
+// NO CHECKED-IN PROTOBUF GENCODE
 // clang-format off
 // source: google/protobuf/wrappers.proto
 
diff --git a/src/google/protobuf/compiler/objectivec/file.cc b/src/google/protobuf/compiler/objectivec/file.cc
index db95c4eefc..fdd0670297 100644
--- a/src/google/protobuf/compiler/objectivec/file.cc
+++ b/src/google/protobuf/compiler/objectivec/file.cc
@@ -598,6 +598,10 @@ void FileGenerator::GenerateFile(io::Printer* p, GeneratedFileType file_type,
 
   p->Emit(
       {
+          {"no_checked_in",
+           "NO CHECKED-IN"
+           // Intentional line breaker
+           " PROTOBUF GENCODE"},
           {"filename", file_->name()},
           {"google_protobuf_objc_version", GOOGLE_PROTOBUF_OBJC_VERSION},
           {"runtime_imports",
@@ -632,6 +636,7 @@ void FileGenerator::GenerateFile(io::Printer* p, GeneratedFileType file_type,
       },
       R"objc(
         // Generated by the protocol buffer compiler.  DO NOT EDIT!
+        // $no_checked_in$
         // $clangfmt$ off
         // source: $filename$