Index: lib/Lex/ModuleMap.cpp
===================================================================
--- lib/Lex/ModuleMap.cpp
+++ lib/Lex/ModuleMap.cpp
@@ -208,9 +208,11 @@
 // Returns true if RequestingModule directly uses RequestedModule.
 static bool directlyUses(const Module *RequestingModule,
                          const Module *RequestedModule) {
-  return std::find(RequestingModule->DirectUses.begin(),
-                   RequestingModule->DirectUses.end(),
-                   RequestedModule) != RequestingModule->DirectUses.end();
+  for (const Module* DirectUse : RequestingModule->DirectUses) {
+    if (RequestedModule->isSubModuleOf(DirectUse))
+      return true;
+  }
+  return false;
 }
 
 static bool violatesPrivateInclude(Module *RequestingModule,
Index: test/Modules/Inputs/declare-use/module.map
===================================================================
--- test/Modules/Inputs/declare-use/module.map
+++ test/Modules/Inputs/declare-use/module.map
@@ -39,6 +39,7 @@
   use XE
   use XJ
   use XK
+  use XN
 }
 
 module XH {
@@ -66,5 +67,11 @@
   textual header "m2.h"
 }
 
+module XN {
+  module sub {
+    header "sub.h"
+  }
+}
+
 module XS {
 }
Index: test/Modules/declare-use1.cpp
===================================================================
--- test/Modules/declare-use1.cpp
+++ test/Modules/declare-use1.cpp
@@ -5,4 +5,5 @@
 #include "e.h"
 #include "f.h" // expected-error {{module XG does not depend on a module exporting 'f.h'}}
 #include "i.h"
-const int g2 = g1 + e + f + aux_i;
+#include "sub.h"
+const int g2 = g1 + e + f + aux_i + sub;