diff --git a/include/clang/Basic/Module.h b/include/clang/Basic/Module.h
index 49be4ec..98f86df 100644
--- a/include/clang/Basic/Module.h
+++ b/include/clang/Basic/Module.h
@@ -123,8 +123,13 @@ public:
   /// will be false to indicate that this (sub)module is not available.
   SmallVector<Requirement, 2> Requirements;
 
-  /// \brief Whether this module is available in the current
-  /// translation unit.
+  /// \brief Whether this module is missing a feature from \c Requirements.
+  unsigned IsMissingRequirement : 1;
+
+  /// \brief Whether this module is available in the current translation unit.
+  ///
+  /// If the module is missing headers or does not meet all requirements then
+  /// this bit will be 0.
   unsigned IsAvailable : 1;
 
   /// \brief Whether this module was loaded from a module file.
@@ -407,6 +412,9 @@ public:
                       const LangOptions &LangOpts,
                       const TargetInfo &Target);
 
+  /// \brief Mark this module and all of its submodules as unavailable.
+  void markUnavailable();
+
   /// \brief Find the submodule with the given name.
   ///
   /// \returns The submodule if found, or NULL otherwise.
diff --git a/lib/Basic/Module.cpp b/lib/Basic/Module.cpp
index d5c02d8..6f29fae 100644
--- a/lib/Basic/Module.cpp
+++ b/lib/Basic/Module.cpp
@@ -160,6 +160,11 @@ void Module::addRequirement(StringRef Feature, bool RequiredState,
   if (hasFeature(Feature, LangOpts, Target) == RequiredState)
     return;
 
+  IsMissingRequirement = true;
+  markUnavailable();
+}
+
+void Module::markUnavailable() {
   if (!IsAvailable)
     return;
 
diff --git a/lib/Frontend/FrontendActions.cpp b/lib/Frontend/FrontendActions.cpp
index 1092c56..3d65ae3 100644
--- a/lib/Frontend/FrontendActions.cpp
+++ b/lib/Frontend/FrontendActions.cpp
@@ -288,7 +288,8 @@ bool GenerateModuleAction::BeginSourceFileAction(CompilerInstance &CI,
   if (!Module->isAvailable(CI.getLangOpts(), CI.getTarget(), Requirement,
                            MissingHeader)) {
     if (MissingHeader.FileNameLoc.isValid()) {
-      CI.getDiagnostics().Report(diag::err_module_header_missing)
+      CI.getDiagnostics().Report(MissingHeader.FileNameLoc,
+                                 diag::err_module_header_missing)
         << MissingHeader.IsUmbrella << MissingHeader.FileName;
     } else {
       CI.getDiagnostics().Report(diag::err_module_unavailable)
diff --git a/lib/Lex/ModuleMap.cpp b/lib/Lex/ModuleMap.cpp
index 27ba762..0e712b0 100644
--- a/lib/Lex/ModuleMap.cpp
+++ b/lib/Lex/ModuleMap.cpp
@@ -1477,6 +1477,15 @@ void ModuleMapParser::parseModuleDecl() {
     inferFrameworkLink(ActiveModule, Directory, SourceMgr.getFileManager());
   }
 
+  // If the module meets all requirements but is still unavailable, mark the
+  // whole tree as unavailable to prevent it from building.
+  if (!ActiveModule->IsAvailable && !ActiveModule->IsMissingRequirement &&
+      ActiveModule->Parent) {
+    ActiveModule->getTopLevelModule()->markUnavailable();
+    ActiveModule->getTopLevelModule()->MissingHeaders.append(
+      ActiveModule->MissingHeaders.begin(), ActiveModule->MissingHeaders.end());
+  }
+
   // We're done parsing this module. Pop back to the previous module.
   ActiveModule = PreviousActiveModule;
 }
@@ -1705,9 +1714,8 @@ void ModuleMapParser::parseHeaderDecl(MMToken::TokenKind LeadingToken,
 
     // If we find a module that has a missing header, we mark this module as
     // unavailable and store the header directive for displaying diagnostics.
-    // Other submodules in the same module can still be used.
     Header.IsUmbrella = LeadingToken == MMToken::UmbrellaKeyword;
-    ActiveModule->IsAvailable = false;
+    ActiveModule->markUnavailable();
     ActiveModule->MissingHeaders.push_back(Header);
   }
 }
diff --git a/test/Modules/Inputs/submodules/module.map b/test/Modules/Inputs/submodules/module.map
index 1593103..8677ea0 100644
--- a/test/Modules/Inputs/submodules/module.map
+++ b/test/Modules/Inputs/submodules/module.map
@@ -15,3 +15,11 @@ module missing_headers {
   module missing { header "missing.h" }
   module not_missing { header "not_missing.h" }
 }
+
+module missing_unavailable_headers {
+  module missing {
+    requires !objc
+    header "missing.h"
+  }
+  module not_missing { }
+}
diff --git a/test/Modules/missing-header.m b/test/Modules/missing-header.m
new file mode 100644
index 0000000..c2c1673
--- /dev/null
+++ b/test/Modules/missing-header.m
@@ -0,0 +1,13 @@
+// RUN: rm -rf %t
+// RUN: not %clang_cc1 -x objective-c -fmodules-cache-path=%t -fmodules -I %S/Inputs/submodules %s 2>&1 | FileCheck %s
+
+// FIXME: cannot use -verify, because the error from inside the module build has
+// a different source manager than the verifier.
+
+@import missing_unavailable_headers; // OK
+@import missing_unavailable_headers.not_missing; // OK
+// CHECK-NOT: missing_unavailable_headers
+
+@import missing_headers;
+// CHECK: module.map:15:27: error: header 'missing.h' not found
+// CHECK: could not build module 'missing_headers'
diff --git a/test/Modules/submodules.cpp b/test/Modules/submodules.cpp
index a18138c..7ef785c 100644
--- a/test/Modules/submodules.cpp
+++ b/test/Modules/submodules.cpp
@@ -32,8 +32,3 @@ extern MyTypeA import_self_test_a; // expected-error {{must be imported from mod
 // expected-note@import-self-a.h:1 {{here}}
 extern MyTypeC import_self_test_c;
 extern MyTypeD import_self_test_d;
-
-// expected-error@Inputs/submodules/module.map:15{{header 'missing.h' not found}}
-@import missing_headers.missing;
-@import missing_headers.not_missing;
-void f() { NotMissingFunction(); };