diff --git a/objectivec/GPBDescriptor_PackagePrivate.h b/objectivec/GPBDescriptor_PackagePrivate.h
index 07c83dc061e33..3c431db10b6d8 100644
--- a/objectivec/GPBDescriptor_PackagePrivate.h
+++ b/objectivec/GPBDescriptor_PackagePrivate.h
@@ -215,14 +215,18 @@ typedef NS_OPTIONS(uint32_t, GPBDescriptorInitializationFlags) {
                                  fields:(void *)fieldDescriptions
                              fieldCount:(uint32_t)fieldCount
                             storageSize:(uint32_t)storageSize
-                                  flags:(GPBDescriptorInitializationFlags)flags;
+                                  flags:(GPBDescriptorInitializationFlags)flags
+    __attribute__((deprecated("Please use a newer version of protoc to regenerate your sources. "
+                              "Support for this version will go away in the future.")));
 + (instancetype)allocDescriptorForClass:(Class)messageClass
                               rootClass:(Class)rootClass
                                    file:(GPBFileDescriptor *)file
                                  fields:(void *)fieldDescriptions
                              fieldCount:(uint32_t)fieldCount
                             storageSize:(uint32_t)storageSize
-                                  flags:(GPBDescriptorInitializationFlags)flags;
+                                  flags:(GPBDescriptorInitializationFlags)flags
+    __attribute__((deprecated("Please use a newer version of protoc to regenerate your sources. "
+                              "Support for this version will go away in the future.")));
 - (void)setupContainingMessageClassName:(const char *)msgClassName;
 - (void)setupMessageClassNameSuffix:(NSString *)suffix;
 
@@ -282,13 +286,17 @@ typedef NS_OPTIONS(uint32_t, GPBEnumDescriptorInitializationFlags) {
                             valueNames:(const char *)valueNames
                                 values:(const int32_t *)values
                                  count:(uint32_t)valueCount
-                          enumVerifier:(GPBEnumValidationFunc)enumVerifier;
+                          enumVerifier:(GPBEnumValidationFunc)enumVerifier
+    __attribute__((deprecated("Please use a newer version of protoc to regenerate your sources. "
+                              "Support for this version will go away in the future.")));
 + (instancetype)allocDescriptorForName:(NSString *)name
                             valueNames:(const char *)valueNames
                                 values:(const int32_t *)values
                                  count:(uint32_t)valueCount
                           enumVerifier:(GPBEnumValidationFunc)enumVerifier
-                   extraTextFormatInfo:(const char *)extraTextFormatInfo;
+                   extraTextFormatInfo:(const char *)extraTextFormatInfo
+    __attribute__((deprecated("Please use a newer version of protoc to regenerate your sources. "
+                              "Support for this version will go away in the future.")));
 @end
 
 @interface GPBExtensionDescriptor () {
@@ -307,7 +315,9 @@ typedef NS_OPTIONS(uint32_t, GPBEnumDescriptorInitializationFlags) {
 - (instancetype)initWithExtensionDescription:(GPBExtensionDescription *)desc
                                usesClassRefs:(BOOL)usesClassRefs;
 // Deprecated. Calls above with `usesClassRefs = NO`
-- (instancetype)initWithExtensionDescription:(GPBExtensionDescription *)desc;
+- (instancetype)initWithExtensionDescription:(GPBExtensionDescription *)desc
+    __attribute__((deprecated("Please use a newer version of protoc to regenerate your sources. "
+                              "Support for this version will go away in the future.")));
 
 - (NSComparisonResult)compareByFieldNumber:(GPBExtensionDescriptor *)other;
 @end
diff --git a/objectivec/GPBMessage.m b/objectivec/GPBMessage.m
index 591ac47bd6884..4b2998fad8f9e 100644
--- a/objectivec/GPBMessage.m
+++ b/objectivec/GPBMessage.m
@@ -1196,18 +1196,19 @@ + (instancetype)alloc {
 + (GPBDescriptor *)descriptor {
   // This is thread safe because it is called from +initialize.
   static GPBDescriptor *descriptor = NULL;
-  static GPBFileDescriptor *fileDescriptor = NULL;
+  static GPBFileDescription fileDescription = {
+      .package = "internal", .prefix = "", .syntax = GPBFileSyntaxProto2};
   if (!descriptor) {
-    fileDescriptor = [[GPBFileDescriptor alloc] initWithPackage:@"internal"
-                                                         syntax:GPBFileSyntaxProto2];
-
-    descriptor = [GPBDescriptor allocDescriptorForClass:[GPBMessage class]
-                                              rootClass:Nil
-                                                   file:fileDescriptor
-                                                 fields:NULL
-                                             fieldCount:0
-                                            storageSize:0
-                                                  flags:0];
+    descriptor = [GPBDescriptor
+        allocDescriptorForClass:[GPBMessage class]
+                    messageName:@"GPBMessage"
+                fileDescription:&fileDescription
+                         fields:NULL
+                     fieldCount:0
+                    storageSize:0
+                          flags:(GPBDescriptorInitializationFlag_UsesClassRefs |
+                                 GPBDescriptorInitializationFlag_Proto3OptionalKnown |
+                                 GPBDescriptorInitializationFlag_ClosedEnumSupportKnown)];
   }
   return descriptor;
 }
diff --git a/objectivec/GPBUtilities.m b/objectivec/GPBUtilities.m
index 0764c96910595..dc6e871aa9908 100644
--- a/objectivec/GPBUtilities.m
+++ b/objectivec/GPBUtilities.m
@@ -206,6 +206,14 @@ void GPBCheckRuntimeVersionSupport(int32_t objcRuntimeVersion) {
                        @" supports back to %d!",
                        objcRuntimeVersion, GOOGLE_PROTOBUF_OBJC_MIN_SUPPORTED_VERSION];
   }
+#if defined(DEBUG) && DEBUG
+  if (objcRuntimeVersion < GOOGLE_PROTOBUF_OBJC_VERSION) {
+    // This is a version we haven't generated for yet.
+    NSLog(@"WARNING: Code from generated Objective-C proto from an older version of the library is "
+          @"being used. Please regenerate with the current version as the code will stop working "
+          @"in a future release.");
+  }
+#endif
 }
 
 void GPBRuntimeMatchFailure(void) {
diff --git a/objectivec/Tests/GPBMessageTests+ClassNames.m b/objectivec/Tests/GPBMessageTests+ClassNames.m
index 3ad5e7167f23a..010fd419eed38 100644
--- a/objectivec/Tests/GPBMessageTests+ClassNames.m
+++ b/objectivec/Tests/GPBMessageTests+ClassNames.m
@@ -14,6 +14,9 @@
 #import "GPBMessage.h"
 #import "GPBRootObject_PackagePrivate.h"
 
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wdeprecated-declarations"
+
 // Support classes for tests using old class name (vs classrefs) interfaces.
 GPB_FINAL @interface MessageLackingClazzRoot : GPBRootObject
 @end
@@ -107,6 +110,8 @@ + (GPBExtensionRegistry *)extensionRegistry {
 }
 @end
 
+#pragma clang diagnostic pop
+
 @interface MessageClassNameTests : GPBTestCase
 @end