diff --git a/include/swift/AST/Decl.h b/include/swift/AST/Decl.h
index ebb751d3027e4..4134902584047 100644
--- a/include/swift/AST/Decl.h
+++ b/include/swift/AST/Decl.h
@@ -2684,8 +2684,29 @@ class ValueDecl : public Decl {
 
   SourceLoc getNameLoc() const { return NameLoc; }
 
+  /// Returns \c true if this value decl is inlinable with attributes
+  /// \c \@usableFromInline, \c \@inlinalbe, and \c \@_alwaysEmitIntoClient
   bool isUsableFromInline() const;
 
+  /// Returns \c true if this value decl needs a special case handling for an
+  /// interface file.
+  ///
+  /// One such case is a reference of an inlinable decl with a `package` access level
+  /// in an interface file as follows: Package decls are only printed in interface files if
+  /// they are inlinable (as defined in \c isUsableFromInline). They could be
+  /// referenced by a module outside of its defining module that belong to the same
+  /// package determined by the `package-name` flag. However, the flag is only in
+  /// .swiftmodule and .private.swiftinterface, thus type checking references of inlinable
+  /// package symbols in public interfaces fails due to the missing flag.
+  /// Instead of adding the package-name flag to the public interfaces, which
+  /// could raise a security concern, we grant access to such cases. 
+  ///
+  /// \sa useDC The use site where this value decl is referenced.
+  /// \sa useAcl The access level of its use site.
+  /// \sa declScope The access scope of this decl site.
+  bool skipAccessCheckIfInterface(const DeclContext *useDC, AccessLevel useAcl,
+                                  AccessScope declScope) const;
+
   /// Returns \c true if this declaration is *not* intended to be used directly
   /// by application developers despite the visibility.
   bool shouldHideFromEditor() const;
diff --git a/lib/AST/Decl.cpp b/lib/AST/Decl.cpp
index 76789e5b96d92..7c5f0485d7323 100644
--- a/lib/AST/Decl.cpp
+++ b/lib/AST/Decl.cpp
@@ -3818,6 +3818,17 @@ bool ValueDecl::isUsableFromInline() const {
   return false;
 }
 
+bool ValueDecl::skipAccessCheckIfInterface(const DeclContext *useDC,
+                                           AccessLevel useAcl,
+                                           AccessScope declScope) const {
+  if (!useDC || useAcl != AccessLevel::Package || !declScope.isPackage() ||
+      !isUsableFromInline() ||
+      getDeclContext()->getParentModule() == useDC->getParentModule())
+    return false;
+  auto useSF = useDC->getParentSourceFile();
+  return useSF && useSF->Kind == SourceFileKind::Interface;
+}
+
 bool ValueDecl::shouldHideFromEditor() const {
   // Hide private stdlib declarations.
   if (isPrivateStdlibDecl(/*treatNonBuiltinProtocolsAsPublic*/ false) ||
@@ -4154,8 +4165,13 @@ static bool checkAccessUsingAccessScopes(const DeclContext *useDC,
       VD, access, useDC,
       /*treatUsableFromInlineAsPublic*/ includeInlineable);
   if (accessScope.getDeclContext() == useDC) return true;
-  if (!AccessScope(useDC).isChildOf(accessScope)) return false;
-
+  if (!AccessScope(useDC).isChildOf(accessScope)) {
+    // Grant access if this VD is an inlinable package decl referenced by
+    // another module in an interface file.
+    if (VD->skipAccessCheckIfInterface(useDC, access, accessScope))
+      return true;
+    return false;
+  }
   // useDC is null only when caller wants to skip non-public type checks.
   if (!useDC) return true;
 
diff --git a/lib/Sema/TypeCheckProtocol.cpp b/lib/Sema/TypeCheckProtocol.cpp
index 839a7be26fddf..9e5ead15d52d4 100644
--- a/lib/Sema/TypeCheckProtocol.cpp
+++ b/lib/Sema/TypeCheckProtocol.cpp
@@ -4372,6 +4372,10 @@ ConformanceChecker::resolveWitnessViaLookup(ValueDecl *requirement) {
           requiredAccessScope.requiredAccessForDiagnostics();
         auto proto = conformance->getProtocol();
         auto protoAccessScope = proto->getFormalAccessScope(DC);
+        // Skip diagnostics of a witness of a package protocol that is inlinalbe
+        // referenced in an interface file.
+        if (proto->skipAccessCheckIfInterface(DC, requiredAccess, protoAccessScope))
+          return;
         bool protoForcesAccess =
           requiredAccessScope.hasEqualDeclContextWith(protoAccessScope);
         auto diagKind = protoForcesAccess
diff --git a/test/Sema/accessibility_package_interface.swift b/test/Sema/accessibility_package_interface.swift
index 6cd2c8bcf1e70..c4679f5753c1e 100644
--- a/test/Sema/accessibility_package_interface.swift
+++ b/test/Sema/accessibility_package_interface.swift
@@ -10,29 +10,118 @@
 // RUN:   -emit-private-module-interface-path %t/Utils.private.swiftinterface
 
 // RUN: %target-swift-typecheck-module-from-interface(%t/Utils.swiftinterface) -I %t
-// RUN: %FileCheck %s --check-prefix=CHECK-PUBLIC < %t/Utils.swiftinterface
-// CHECK-PUBLIC-NOT: -package-name swift-utils.log
-// CHECK-PUBLIC-NOT: package func packageFunc()
-// CHECK-PUBLIC: -module-name Utils
-// CHECK-PUBLIC: public func publicFunc()
+// RUN: %FileCheck %s --check-prefix=CHECK-PUBLIC-UTILS < %t/Utils.swiftinterface
+
+// CHECK-PUBLIC-UTILS-NOT: -package-name swift-utils.log
+// CHECK-PUBLIC-UTILS-NOT: package func packageFunc()
+// CHECK-PUBLIC-UTILS-NOT: package protocol PackageProto
+// CHECK-PUBLIC-UTILS-NOT: var pkgVar
+// CHECK-PUBLIC-UTILS-NOT: package class PackageKlass
+// CHECK-PUBLIC-UTILS-NOT: package var pkgVar
+// CHECK-PUBLIC-UTILS: -module-name Utils
+// CHECK-PUBLIC-UTILS: public func publicFunc()
+// CHECK-PUBLIC-UTILS: @usableFromInline
+// CHECK-PUBLIC-UTILS: package func ufiPackageFunc()
+// CHECK-PUBLIC-UTILS: @usableFromInline
+// CHECK-PUBLIC-UTILS: package protocol UfiPackageProto
+// CHECK-PUBLIC-UTILS: var ufiPkgVar
+// CHECK-PUBLIC-UTILS: @usableFromInline
+// CHECK-PUBLIC-UTILS: package class UfiPackageKlass
+// CHECK-PUBLIC-UTILS: @usableFromInline
+// CHECK-PUBLIC-UTILS: package var ufiPkgVar
 
 // RUN: %target-swift-typecheck-module-from-interface(%t/Utils.private.swiftinterface) -module-name Utils -I %t
-// RUN: %FileCheck %s --check-prefix=CHECK-PRIVATE < %t/Utils.private.swiftinterface
+// RUN: %FileCheck %s --check-prefix=CHECK-PRIVATE-UTILS < %t/Utils.private.swiftinterface
+
+// CHECK-PRIVATE-UTILS-NOT: package func packageFunc()
+// CHECK-PRIVATE-UTILS-NOT: package protocol PackageProto
+// CHECK-PRIVATE-UTILS-NOT: var pkgVar
+// CHECK-PRIVATE-UTILS-NOT: package class PackageKlass
+// CHECK-PRIVATE-UTILS-NOT: package var pkgVar
+// CHECK-PRIVATE-UTILS: -module-name Utils
+// CHECK-PRIVATE-UTILS: swift-module-flags-ignorable-private: -package-name swift-utils.log
+// CHECK-PRIVATE-UTILS: public func publicFunc()
+// CHECK-PRIVATE-UTILS: @usableFromInline
+// CHECK-PRIVATE-UTILS: package func ufiPackageFunc()
+// CHECK-PRIVATE-UTILS: @usableFromInline
+// CHECK-PRIVATE-UTILS: package protocol UfiPackageProto
+// CHECK-PRIVATE-UTILS: var ufiPkgVar
+// CHECK-PRIVATE-UTILS: @usableFromInline
+// CHECK-PRIVATE-UTILS: package class UfiPackageKlass
+// CHECK-PRIVATE-UTILS: @usableFromInline
+// CHECK-PRIVATE-UTILS: package var ufiPkgVar
+
+// RUN: %target-swift-frontend -emit-module %t/Client.swift \
+// RUN:   -module-name Client -swift-version 5 -I %t \
+// RUN:   -package-name swift-utils.log \
+// RUN:   -enable-library-evolution \
+// RUN:   -emit-module-path %t/Client.swiftmodule \
+// RUN:   -emit-module-interface-path %t/Client.swiftinterface \
+// RUN:   -emit-private-module-interface-path %t/Client.private.swiftinterface
+
+// RUN: rm -rf %t/Utils.swiftmodule
+// RUN: rm -rf %t/Client.swiftmodule
 
-// CHECK-PRIVATE-NOT: package func packageFunc()
-// CHECK-PRIVATE: swift-module-flags-ignorable-private: -package-name swift-utils.log
-// CHECK-PRIVATE: public func publicFunc()
+// RUN: %target-swift-typecheck-module-from-interface(%t/Client.swiftinterface) -I %t -verify
+// RUN: %FileCheck %s --check-prefix=CHECK-PUBLIC-CLIENT < %t/Client.swiftinterface
+// CHECK-PUBLIC-CLIENT-NOT: -package-name swift-utils.log
+// CHECK-PUBLIC-CLIENT: @inlinable public func clientFunc()
+// CHECK-PUBLIC-CLIENT: publicFunc()
+// CHECK-PUBLIC-CLIENT: ufiPackageFunc()
+// CHECK-PUBLIC-CLIENT: let u = UfiPackageKlass()
+// CHECK-PUBLIC-CLIENT: return u.ufiPkgVar
+// CHECK-PUBLIC-CLIENT: public class ClientKlass1 : Utils.UfiPackageProto
+// CHECK-PUBLIC-CLIENT: @usableFromInline
+// CHECK-PUBLIC-CLIENT: package var ufiPkgVar: Swift.String
+// CHECK-PUBLIC-CLIENT: public class ClientKlass2 : Utils.UfiPackageProto
+// CHECK-PUBLIC-CLIENT: public var ufiPkgVar: Swift.String
+
+// RUN: %target-swift-typecheck-module-from-interface(%t/Client.private.swiftinterface) -module-name Client -I %t -verify
 
-// RUN: %target-swift-frontend -typecheck %t/Client.swift -package-name swift-utils.log -I %t -verify
 
 //--- Utils.swift
-package func packageFunc() {}
 public func publicFunc() {}
 
+package func packageFunc() {}
+@usableFromInline
+package func ufiPackageFunc() {}
+
+package protocol PackageProto {
+  var pkgVar: String { get set }
+}
+package class PackageKlass: PackageProto {
+  package var pkgVar = ""
+}
+
+@usableFromInline
+package protocol UfiPackageProto {
+  var ufiPkgVar: String { get set }
+}
+
+@usableFromInline
+package class UfiPackageKlass: UfiPackageProto {
+  @usableFromInline
+  package init() {}
+  @usableFromInline
+  package var ufiPkgVar = ""
+}
+
+
 //--- Client.swift
 import Utils
 
-func clientFunc() {
-  packageFunc()
+@inlinable public func clientFunc() -> String {
   publicFunc()
+  ufiPackageFunc()
+  let u = UfiPackageKlass()
+  return u.ufiPkgVar
+}
+
+public class ClientKlass1: UfiPackageProto {
+  @usableFromInline
+  package var ufiPkgVar = "B"
+}
+
+public class ClientKlass2: UfiPackageProto {
+  public var ufiPkgVar = "C"
 }