diff --git a/include/swift/AST/DiagnosticsSema.def b/include/swift/AST/DiagnosticsSema.def
index 5227dfa4e7c46..b3b32591277a5 100644
--- a/include/swift/AST/DiagnosticsSema.def
+++ b/include/swift/AST/DiagnosticsSema.def
@@ -782,6 +782,9 @@ ERROR(serialization_name_mismatch_repl,none,
 ERROR(serialization_target_incompatible,Fatal,
       "module %0 was created for incompatible target %1: %2",
       (Identifier, StringRef, StringRef))
+ERROR(serialization_sdk_mismatch,Fatal,
+      "cannot load module %0 built with SDK '%1' when using SDK '%2': %3",
+      (Identifier, StringRef, StringRef, StringRef))
 ERROR(serialization_target_incompatible_repl,none,
       "module %0 was created for incompatible target %1: %2",
       (Identifier, StringRef, StringRef))
diff --git a/include/swift/AST/SearchPathOptions.h b/include/swift/AST/SearchPathOptions.h
index f873e82ada368..02f61eadfe59a 100644
--- a/include/swift/AST/SearchPathOptions.h
+++ b/include/swift/AST/SearchPathOptions.h
@@ -82,6 +82,10 @@ class SearchPathOptions {
   /// would for a non-system header.
   bool DisableModulesValidateSystemDependencies = false;
 
+  /// Enforce loading only serialized modules built with the same SDK
+  /// as the context loading it.
+  bool EnableSameSDKCheck = true;
+
   /// A set of compiled modules that may be ready to use.
   std::vector<std::string> CandidateCompiledModules;
 
diff --git a/include/swift/Basic/LangOptions.h b/include/swift/Basic/LangOptions.h
index f8d161d346e51..6d14419be809c 100644
--- a/include/swift/Basic/LangOptions.h
+++ b/include/swift/Basic/LangOptions.h
@@ -127,6 +127,9 @@ namespace swift {
     /// The target variant SDK version, if known.
     Optional<llvm::VersionTuple> VariantSDKVersion;
 
+    /// The SDK canonical name, if known.
+    std::string SDKName;
+
     /// The alternate name to use for the entry point instead of main.
     std::string entryPointFunctionName = "main";
 
diff --git a/include/swift/Option/FrontendOptions.td b/include/swift/Option/FrontendOptions.td
index 0097ea215f0ff..7ea2ec76be348 100644
--- a/include/swift/Option/FrontendOptions.td
+++ b/include/swift/Option/FrontendOptions.td
@@ -823,6 +823,9 @@ def target_sdk_version : Separate<["-"], "target-sdk-version">,
 def target_variant_sdk_version : Separate<["-"], "target-variant-sdk-version">,
   HelpText<"The version of target variant SDK used for compilation">;
 
+def target_sdk_name : Separate<["-"], "target-sdk-name">,
+  HelpText<"Canonical name of the target SDK used for compilation">;
+
 def extra_clang_options_only : Flag<["-"], "only-use-extra-clang-opts">,
   HelpText<"Options passed via -Xcc are sufficient for Clang configuration">;
 
diff --git a/include/swift/Serialization/SerializationOptions.h b/include/swift/Serialization/SerializationOptions.h
index 2b180591a19d7..8f19f7d9ed22d 100644
--- a/include/swift/Serialization/SerializationOptions.h
+++ b/include/swift/Serialization/SerializationOptions.h
@@ -35,6 +35,7 @@ namespace swift {
     bool SkipSymbolGraphInheritedDocs = true;
     bool IncludeSPISymbolsInSymbolGraph = false;
     llvm::VersionTuple UserModuleVersion;
+    std::string SDKName;
 
     StringRef GroupInfoPath;
     StringRef ImportedHeader;
diff --git a/include/swift/Serialization/Validation.h b/include/swift/Serialization/Validation.h
index e5564a139473d..a2ffe970ed987 100644
--- a/include/swift/Serialization/Validation.h
+++ b/include/swift/Serialization/Validation.h
@@ -66,7 +66,11 @@ enum class Status {
   TargetIncompatible,
 
   /// The module file was built for a target newer than the current target.
-  TargetTooNew
+  TargetTooNew,
+
+  /// The module file was built with a different SDK than the one in use
+  /// to build the client.
+  SDKMismatch
 };
 
 /// Returns true if the data looks like it contains a serialized AST.
@@ -80,6 +84,7 @@ struct ValidationInfo {
   StringRef miscVersion = {};
   version::Version compatibilityVersion = {};
   llvm::VersionTuple userModuleVersion;
+  StringRef sdkName = {};
   size_t bytes = 0;
   Status status = Status::Malformed;
 };
diff --git a/lib/APIDigester/ModuleAnalyzerNodes.cpp b/lib/APIDigester/ModuleAnalyzerNodes.cpp
index c9b9fa9837f14..cd59b02dbffe0 100644
--- a/lib/APIDigester/ModuleAnalyzerNodes.cpp
+++ b/lib/APIDigester/ModuleAnalyzerNodes.cpp
@@ -2233,6 +2233,9 @@ swift::ide::api::getSDKNodeRoot(SDKContext &SDKCtx,
 
   auto &Ctx = CI.getASTContext();
 
+  // Don't check if the stdlib was build with the same SDK as what is loaded
+  // here as some tests rely on using a different stdlib.
+  Ctx.SearchPathOpts.EnableSameSDKCheck = false;
 
   // Load standard library so that Clang importer can use it.
   auto *Stdlib = Ctx.getStdlibModule(/*loadIfAbsent=*/true);
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index a854fc85e2dec..4c740f3cb4a00 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -774,6 +774,11 @@ static bool ParseLangArgs(LangOptions &Opts, ArgList &Args,
     }
   }
 
+  // Get the SDK name.
+  if (Arg *A = Args.getLastArg(options::OPT_target_sdk_name)) {
+    Opts.SDKName = A->getValue();
+  }
+
   if (const Arg *A = Args.getLastArg(OPT_entry_point_function_name)) {
     Opts.entryPointFunctionName = A->getValue();
   }
diff --git a/lib/Frontend/Frontend.cpp b/lib/Frontend/Frontend.cpp
index de292051246f9..685974fb55471 100644
--- a/lib/Frontend/Frontend.cpp
+++ b/lib/Frontend/Frontend.cpp
@@ -150,6 +150,7 @@ SerializationOptions CompilerInvocation::computeSerializationOptions(
   serializationOpts.ExtraClangOptions = getClangImporterOptions().ExtraArgs;
   serializationOpts.PublicDependentLibraries =
       getIRGenOptions().PublicLinkLibraries;
+  serializationOpts.SDKName = getLangOptions().SDKName;
 
   if (opts.EmitSymbolGraph) {
     if (!opts.SymbolGraphOutputDir.empty()) {
diff --git a/lib/Frontend/ModuleInterfaceBuilder.cpp b/lib/Frontend/ModuleInterfaceBuilder.cpp
index 4c8a3e18579da..19a3240826c5b 100644
--- a/lib/Frontend/ModuleInterfaceBuilder.cpp
+++ b/lib/Frontend/ModuleInterfaceBuilder.cpp
@@ -257,6 +257,8 @@ bool ModuleInterfaceBuilder::buildSwiftModuleInternal(
     if (!getRelativeDepPath(InPath, SDKPath))
       SerializationOpts.ModuleInterface = InPath;
 
+    SerializationOpts.SDKName = SubInstance.getASTContext().LangOpts.SDKName;
+
     SmallVector<FileDependency, 16> Deps;
     bool serializeHashes = FEOpts.SerializeModuleInterfaceDependencyHashes;
     if (collectDepsForSerialization(SubInstance, Deps, serializeHashes)) {
diff --git a/lib/Serialization/ModuleFile.cpp b/lib/Serialization/ModuleFile.cpp
index 1d2aeeb027679..38990f4b4e4c5 100644
--- a/lib/Serialization/ModuleFile.cpp
+++ b/lib/Serialization/ModuleFile.cpp
@@ -149,6 +149,15 @@ Status ModuleFile::associateWithFileContext(FileUnit *file, SourceLoc diagLoc,
       return error(status);
   }
 
+  auto clientSDK = ctx.LangOpts.SDKName;
+  StringRef moduleSDK = Core->SDKName;
+  if (ctx.SearchPathOpts.EnableSameSDKCheck &&
+      !moduleSDK.empty() && !clientSDK.empty() &&
+      moduleSDK != clientSDK) {
+    status = Status::SDKMismatch;
+    return error(status);
+  }
+
   for (const auto &searchPath : Core->SearchPaths)
     ctx.addSearchPath(searchPath.Path, searchPath.IsFramework,
                       searchPath.IsSystem);
diff --git a/lib/Serialization/ModuleFileSharedCore.cpp b/lib/Serialization/ModuleFileSharedCore.cpp
index 8fba7e2ed85b1..eeec9a2fef78b 100644
--- a/lib/Serialization/ModuleFileSharedCore.cpp
+++ b/lib/Serialization/ModuleFileSharedCore.cpp
@@ -299,6 +299,10 @@ validateControlBlock(llvm::BitstreamCursor &cursor,
     case control_block::TARGET:
       result.targetTriple = blobData;
       break;
+    case control_block::SDK_NAME: {
+      result.sdkName = blobData;
+      break;
+    }
     default:
       // Unknown metadata record, possibly for use by a future version of the
       // module format.
@@ -1210,6 +1214,7 @@ ModuleFileSharedCore::ModuleFileSharedCore(
       }
       Name = info.name;
       TargetTriple = info.targetTriple;
+      SDKName = info.sdkName;
       CompatibilityVersion = info.compatibilityVersion;
       UserModuleVersion = info.userModuleVersion;
       Bits.ArePrivateImportsEnabled = extInfo.arePrivateImportsEnabled();
diff --git a/lib/Serialization/ModuleFileSharedCore.h b/lib/Serialization/ModuleFileSharedCore.h
index e192013c596fc..7f8fde8b28461 100644
--- a/lib/Serialization/ModuleFileSharedCore.h
+++ b/lib/Serialization/ModuleFileSharedCore.h
@@ -58,6 +58,9 @@ class ModuleFileSharedCore {
   /// The target the module was built for.
   StringRef TargetTriple;
 
+  /// The canonical name of the SDK the module was built with.
+  StringRef SDKName;
+
   /// The name of the module interface this module was compiled from.
   ///
   /// Empty if this module didn't come from an interface file.
diff --git a/lib/Serialization/ModuleFormat.h b/lib/Serialization/ModuleFormat.h
index 599ef3e5c0570..18e9530e8612e 100644
--- a/lib/Serialization/ModuleFormat.h
+++ b/lib/Serialization/ModuleFormat.h
@@ -56,7 +56,7 @@ const uint16_t SWIFTMODULE_VERSION_MAJOR = 0;
 /// describe what change you made. The content of this comment isn't important;
 /// it just ensures a conflict if two people change the module format.
 /// Don't worry about adhering to the 80-column limit for this line.
-const uint16_t SWIFTMODULE_VERSION_MINOR = 628; // unaligned pointer
+const uint16_t SWIFTMODULE_VERSION_MINOR = 629; // BuilderSDK
 
 /// A standard hash seed used for all string hashes in a serialized module.
 ///
@@ -754,7 +754,8 @@ namespace control_block {
   enum {
     METADATA = 1,
     MODULE_NAME,
-    TARGET
+    TARGET,
+    SDK_NAME
   };
 
   using MetadataLayout = BCRecordLayout<
@@ -779,6 +780,11 @@ namespace control_block {
     TARGET,
     BCBlob // LLVM triple
   >;
+
+  using SDKNameLayout = BCRecordLayout<
+    SDK_NAME,
+    BCBlob
+  >;
 }
 
 /// The record types within the options block (a sub-block of the control
diff --git a/lib/Serialization/Serialization.cpp b/lib/Serialization/Serialization.cpp
index 92ce769c8851b..0720a001b724f 100644
--- a/lib/Serialization/Serialization.cpp
+++ b/lib/Serialization/Serialization.cpp
@@ -802,6 +802,7 @@ void Serializer::writeBlockInfoBlock() {
   BLOCK_RECORD(control_block, METADATA);
   BLOCK_RECORD(control_block, MODULE_NAME);
   BLOCK_RECORD(control_block, TARGET);
+  BLOCK_RECORD(control_block, SDK_NAME);
 
   BLOCK(OPTIONS_BLOCK);
   BLOCK_RECORD(options_block, SDK_PATH);
@@ -952,6 +953,7 @@ void Serializer::writeHeader(const SerializationOptions &options) {
     control_block::ModuleNameLayout ModuleName(Out);
     control_block::MetadataLayout Metadata(Out);
     control_block::TargetLayout Target(Out);
+    control_block::SDKNameLayout SDKName(Out);
 
     ModuleName.emit(ScratchRecord, M->getName().str());
 
@@ -985,6 +987,9 @@ void Serializer::writeHeader(const SerializationOptions &options) {
                   userModuleSubminor, userModuleBuild,
                   versionString.str());
 
+    if (!options.SDKName.empty())
+      SDKName.emit(ScratchRecord, options.SDKName);
+
     Target.emit(ScratchRecord, M->getASTContext().LangOpts.Target.str());
 
     {
diff --git a/lib/Serialization/SerializedModuleLoader.cpp b/lib/Serialization/SerializedModuleLoader.cpp
index 57c3443143717..5d5dac786cd21 100644
--- a/lib/Serialization/SerializedModuleLoader.cpp
+++ b/lib/Serialization/SerializedModuleLoader.cpp
@@ -976,6 +976,13 @@ void swift::serialization::diagnoseSerializedASTLoadFailure(
                        moduleOSInfo.second, moduleBufferID);
     break;
   }
+
+  case serialization::Status::SDKMismatch:
+    auto currentSDK = Ctx.LangOpts.SDKName;
+    auto moduleSDK = loadInfo.sdkName;
+    Ctx.Diags.diagnose(diagLoc, diag::serialization_sdk_mismatch,
+                       ModuleName, moduleSDK, currentSDK, moduleBufferID);
+    break;
   }
 }
 
diff --git a/test/DebugInfo/compileunit-sysroot-sdk.swift b/test/DebugInfo/compileunit-sysroot-sdk.swift
index 0000a5f50e58d..283616f480b5b 100644
--- a/test/DebugInfo/compileunit-sysroot-sdk.swift
+++ b/test/DebugInfo/compileunit-sysroot-sdk.swift
@@ -1,4 +1,4 @@
-// RUN: %target-swift-frontend %s -emit-ir -g -o - \
+// RUN: %target-swift-frontend %s -emit-ir -g -o - -parse-stdlib \
 // RUN:    -sdk /SWIFT_SYSROOT/MacOSX.sdk | %FileCheck %s
 // Test that sysroot and SDK are stored in the debug info.
 // CHECK: distinct !DICompileUnit({{.*}}sysroot: "/SWIFT_SYSROOT/MacOSX.sdk",
diff --git a/test/Serialization/restrict-swiftmodule-to-sdk.swift b/test/Serialization/restrict-swiftmodule-to-sdk.swift
new file mode 100644
index 0000000000000..5c678fe70a3a8
--- /dev/null
+++ b/test/Serialization/restrict-swiftmodule-to-sdk.swift
@@ -0,0 +1,20 @@
+// RUN: %empty-directory(%t/cache)
+// RUN: %empty-directory(%t/build)
+// RUN: %{python} %utils/split_file.py -o %t %s
+
+/// Build Lib against SDK A.
+// RUN: %target-swift-frontend -emit-module %t/Lib.swift -swift-version 5 -target-sdk-name A -o %t/build -parse-stdlib -module-cache-path %t/cache
+
+/// Building Client against SDK A should work fine as expected.
+// RUN: %target-swift-frontend -typecheck %t/Client.swift -swift-version 5 -target-sdk-name A -I %t/build -parse-stdlib -module-cache-path %t/cache
+
+/// Build Client against SDK B, this should fail at loading Lib against a different SDK than A.
+// RUN: not %target-swift-frontend -typecheck %t/Client.swift -swift-version 5 -target-sdk-name B -I %t/build -parse-stdlib -module-cache-path %t/cache 2>&1 | %FileCheck %s
+// CHECK: cannot load module 'Lib' built with SDK 'A' when using SDK 'B': {{.*}}Lib.swiftmodule
+
+// BEGIN Lib.swift
+public func foo() {}
+
+// BEGIN Client.swift
+import Lib
+foo()
diff --git a/test/api-digester/Inputs/mock-sdk-baseline.sdk/System/Library/Frameworks/SwiftFoo.framework/Modules/SwiftFoo.swiftmodule/arm64-apple-macos.swiftinterface b/test/api-digester/Inputs/mock-sdk-baseline.sdk/System/Library/Frameworks/SwiftFoo.framework/Modules/SwiftFoo.swiftmodule/arm64-apple-macos.swiftinterface
index 04fba0eeed4da..851f24ce52b03 100644
--- a/test/api-digester/Inputs/mock-sdk-baseline.sdk/System/Library/Frameworks/SwiftFoo.framework/Modules/SwiftFoo.swiftmodule/arm64-apple-macos.swiftinterface
+++ b/test/api-digester/Inputs/mock-sdk-baseline.sdk/System/Library/Frameworks/SwiftFoo.framework/Modules/SwiftFoo.swiftmodule/arm64-apple-macos.swiftinterface
@@ -1,7 +1,6 @@
 // swift-interface-format-version: 1.0
 // swift-tools-version: Apple Swift version 5.1 (swiftlang-1100.0.38 clang-1100.0.20.14)
-// swift-module-flags: -target arm64-apple-macos10.14 -enable-objc-interop -enable-library-evolution -swift-version 5 -enforce-exclusivity=checked -O -module-name SwiftFoo
-import Swift
+// swift-module-flags: -target arm64-apple-macos10.14 -enable-objc-interop -enable-library-evolution -swift-version 5 -enforce-exclusivity=checked -O -module-name SwiftFoo -parse-stdlib
 public class RemovedClass {
   @objc deinit
 }
diff --git a/test/api-digester/Inputs/mock-sdk-baseline.sdk/System/Library/Frameworks/SwiftFoo.framework/Modules/SwiftFoo.swiftmodule/x86_64-apple-macos.swiftinterface b/test/api-digester/Inputs/mock-sdk-baseline.sdk/System/Library/Frameworks/SwiftFoo.framework/Modules/SwiftFoo.swiftmodule/x86_64-apple-macos.swiftinterface
index 5dd2912092b75..616271689153f 100644
--- a/test/api-digester/Inputs/mock-sdk-baseline.sdk/System/Library/Frameworks/SwiftFoo.framework/Modules/SwiftFoo.swiftmodule/x86_64-apple-macos.swiftinterface
+++ b/test/api-digester/Inputs/mock-sdk-baseline.sdk/System/Library/Frameworks/SwiftFoo.framework/Modules/SwiftFoo.swiftmodule/x86_64-apple-macos.swiftinterface
@@ -1,7 +1,6 @@
 // swift-interface-format-version: 1.0
 // swift-tools-version: Apple Swift version 5.1 (swiftlang-1100.0.38 clang-1100.0.20.14)
-// swift-module-flags: -target x86_64-apple-macos10.14 -enable-objc-interop -enable-library-evolution -swift-version 5 -enforce-exclusivity=checked -O -module-name SwiftFoo
-import Swift
+// swift-module-flags: -target x86_64-apple-macos10.14 -enable-objc-interop -enable-library-evolution -swift-version 5 -enforce-exclusivity=checked -O -module-name SwiftFoo -parse-stdlib
 public class RemovedClass {
   @objc deinit
 }
diff --git a/test/api-digester/Inputs/mock-sdk.sdk/System/Library/Frameworks/SwiftFoo.framework/Modules/SwiftFoo.swiftmodule/arm64-apple-macos.swiftinterface b/test/api-digester/Inputs/mock-sdk.sdk/System/Library/Frameworks/SwiftFoo.framework/Modules/SwiftFoo.swiftmodule/arm64-apple-macos.swiftinterface
index 606b8bd222422..f20e4f4217a6c 100644
--- a/test/api-digester/Inputs/mock-sdk.sdk/System/Library/Frameworks/SwiftFoo.framework/Modules/SwiftFoo.swiftmodule/arm64-apple-macos.swiftinterface
+++ b/test/api-digester/Inputs/mock-sdk.sdk/System/Library/Frameworks/SwiftFoo.framework/Modules/SwiftFoo.swiftmodule/arm64-apple-macos.swiftinterface
@@ -1,7 +1,6 @@
 // swift-interface-format-version: 1.0
 // swift-tools-version: Apple Swift version 5.1 (swiftlang-1100.0.38 clang-1100.0.20.14)
-// swift-module-flags: -target arm64-apple-macos10.14 -enable-objc-interop -enable-library-evolution -swift-version 5 -enforce-exclusivity=checked -O -module-name SwiftFoo
-import Swift
+// swift-module-flags: -target arm64-apple-macos10.14 -enable-objc-interop -enable-library-evolution -swift-version 5 -enforce-exclusivity=checked -O -module-name SwiftFoo -parse-stdlib
 public class AddedClass {
   @objc deinit
 }
diff --git a/test/api-digester/Inputs/mock-sdk.sdk/System/Library/Frameworks/SwiftFoo.framework/Modules/SwiftFoo.swiftmodule/x86_64-apple-macos.swiftinterface b/test/api-digester/Inputs/mock-sdk.sdk/System/Library/Frameworks/SwiftFoo.framework/Modules/SwiftFoo.swiftmodule/x86_64-apple-macos.swiftinterface
index 3bc9676211a66..5315e1537ee54 100644
--- a/test/api-digester/Inputs/mock-sdk.sdk/System/Library/Frameworks/SwiftFoo.framework/Modules/SwiftFoo.swiftmodule/x86_64-apple-macos.swiftinterface
+++ b/test/api-digester/Inputs/mock-sdk.sdk/System/Library/Frameworks/SwiftFoo.framework/Modules/SwiftFoo.swiftmodule/x86_64-apple-macos.swiftinterface
@@ -1,7 +1,6 @@
 // swift-interface-format-version: 1.0
 // swift-tools-version: Apple Swift version 5.1 (swiftlang-1100.0.38 clang-1100.0.20.14)
-// swift-module-flags: -target x86_64-apple-macos10.14 -enable-objc-interop -enable-library-evolution -swift-version 5 -enforce-exclusivity=checked -O -module-name SwiftFoo
-import Swift
+// swift-module-flags: -target x86_64-apple-macos10.14 -enable-objc-interop -enable-library-evolution -swift-version 5 -enforce-exclusivity=checked -O -module-name SwiftFoo -parse-stdlib
 public class AddedClass {
   @objc deinit
 }