diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -161,12 +161,14 @@
 
 namespace {
 
-std::set<const FileEntry *> GetAffectingModuleMaps(const HeaderSearch &HS,
+std::set<const FileEntry *> GetAffectingModuleMaps(const Preprocessor &PP,
                                                    Module *RootModule) {
   std::set<const FileEntry *> ModuleMaps{};
   std::set<const Module *> ProcessedModules;
   SmallVector<const Module *> ModulesToProcess{RootModule};
 
+  const HeaderSearch &HS = PP.getHeaderSearchInfo();
+
   SmallVector<const FileEntry *, 16> FilesByUID;
   HS.getFileMgr().GetUniqueIDMapping(FilesByUID);
 
@@ -191,12 +193,27 @@
   }
 
   const ModuleMap &MM = HS.getModuleMap();
+  SourceManager &SourceMgr = PP.getSourceManager();
+
+  auto ForIncludeChain = [&](FileEntryRef F,
+                             llvm::function_ref<void(FileEntryRef)> CB) {
+    CB(F);
+    FileID FID = SourceMgr.translateFile(F);
+    SourceLocation Loc = SourceMgr.getIncludeLoc(FID);
+    while (Loc.isValid()) {
+      FID = SourceMgr.getFileID(Loc);
+      CB(*SourceMgr.getFileEntryRefForID(FID));
+      Loc = SourceMgr.getIncludeLoc(FID);
+    }
+  };
 
   auto ProcessModuleOnce = [&](const Module *M) {
     for (const Module *Mod = M; Mod; Mod = Mod->Parent)
       if (ProcessedModules.insert(Mod).second)
         if (auto ModuleMapFile = MM.getModuleMapFileForUniquing(Mod))
-          ModuleMaps.insert(*ModuleMapFile);
+          ForIncludeChain(*ModuleMapFile, [&](FileEntryRef F) {
+            ModuleMaps.insert(F);
+          });
   };
 
   for (const Module *CurrentModule : ModulesToProcess) {
@@ -4545,8 +4562,7 @@
   if (!WritingModule)
     return;
 
-  auto AffectingModuleMaps =
-      GetAffectingModuleMaps(PP->getHeaderSearchInfo(), WritingModule);
+  auto AffectingModuleMaps = GetAffectingModuleMaps(*PP, WritingModule);
 
   unsigned FileIDAdjustment = 0;
   unsigned OffsetAdjustment = 0;
diff --git a/clang/test/ClangScanDeps/modules-extern-unrelated.m b/clang/test/ClangScanDeps/modules-extern-unrelated.m
new file mode 100644
--- /dev/null
+++ b/clang/test/ClangScanDeps/modules-extern-unrelated.m
@@ -0,0 +1,135 @@
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+
+//--- tu.m
+@import zeroth;
+
+//--- zeroth/module.modulemap
+module zeroth { header "zeroth.h" }
+//--- zeroth/zeroth.h
+@import first;
+#include "second.h"
+
+//--- first/module.modulemap
+module first {}
+module first_other { header "first_other.h" }
+//--- first/first_other.h
+
+//--- second/module.modulemap
+extern module second "second.modulemap"
+//--- second/second.modulemap
+module second { header "second.h" }
+//--- second/second.h
+#include "first_other.h"
+
+//--- cdb.json.template
+[{
+  "directory": "DIR",
+  "file": "DIR/tu.m",
+  "command": "clang -fmodules -fmodules-cache-path=DIR/cache -I DIR/zeroth -I DIR/first -I DIR/second -c DIR/tu.m -o DIR/tu.o"
+}]
+
+// RUN: sed -e "s|DIR|%/t|g" -e "s|INPUTS|%/S/Inputs|g" %t/cdb.json.template > %t/cdb.json
+// RUN: clang-scan-deps -compilation-database %t/cdb.json -format experimental-full > %t/result.json
+// RUN: cat %t/result.json | sed 's:\\\\\?:/:g' | FileCheck %s -DPREFIX=%/t
+
+// CHECK:      {
+// CHECK-NEXT:   "modules": [
+// CHECK-NEXT:     {
+// CHECK-NEXT:       "clang-module-deps": [],
+// CHECK-NEXT:       "clang-modulemap-file": "[[PREFIX]]/first/module.modulemap",
+// CHECK-NEXT:       "command-line": [
+// CHECK:            ],
+// CHECK-NEXT:       "context-hash": "{{.*}}",
+// CHECK-NEXT:       "file-deps": [
+// CHECK-NEXT:         "[[PREFIX]]/first/module.modulemap"
+// CHECK-NEXT:       ],
+// CHECK-NEXT:       "name": "first"
+// CHECK-NEXT:     },
+// CHECK-NEXT:     {
+// CHECK-NEXT:       "clang-module-deps": [],
+// CHECK-NEXT:       "clang-modulemap-file": "[[PREFIX]]/first/module.modulemap",
+// CHECK-NEXT:       "command-line": [
+// CHECK:            ],
+// CHECK-NEXT:       "context-hash": "{{.*}}",
+// CHECK-NEXT:       "file-deps": [
+// CHECK-NEXT:         "[[PREFIX]]/first/first_other.h",
+// CHECK-NEXT:         "[[PREFIX]]/first/module.modulemap"
+// CHECK-NEXT:       ],
+// CHECK-NEXT:       "name": "first_other"
+// CHECK-NEXT:     },
+// CHECK-NEXT:     {
+// CHECK-NEXT:       "clang-module-deps": [
+// CHECK-NEXT:         {
+// CHECK-NEXT:           "context-hash": "{{.*}}",
+// CHECK-NEXT:           "module-name": "first_other"
+// CHECK-NEXT:         }
+// CHECK-NEXT:       ],
+// CHECK-NEXT:       "clang-modulemap-file": "[[PREFIX]]/second/second.modulemap",
+// CHECK-NEXT:       "command-line": [
+// CHECK:            ],
+// CHECK-NEXT:       "context-hash": "{{.*}}",
+// CHECK-NEXT:       "file-deps": [
+// CHECK-NEXT:         "[[PREFIX]]/first/module.modulemap",
+// CHECK-NEXT:         "[[PREFIX]]/second/second.h",
+// CHECK-NEXT:         "[[PREFIX]]/second/second.modulemap"
+// CHECK-NEXT:       ],
+// CHECK-NEXT:       "name": "second"
+// CHECK-NEXT:     },
+// CHECK-NEXT:     {
+// CHECK-NEXT:       "clang-module-deps": [
+// CHECK-NEXT:         {
+// CHECK-NEXT:           "context-hash": "{{.*}}",
+// CHECK-NEXT:           "module-name": "first"
+// CHECK-NEXT:         },
+// CHECK-NEXT:         {
+// CHECK-NEXT:           "context-hash": "{{.*}}",
+// CHECK-NEXT:           "module-name": "second"
+// CHECK-NEXT:         }
+// CHECK-NEXT:       ],
+// CHECK-NEXT:       "clang-modulemap-file": "[[PREFIX]]/zeroth/module.modulemap",
+// CHECK-NEXT:       "command-line": [
+// CHECK:            ],
+// CHECK-NEXT:       "context-hash": "{{.*}}",
+// CHECK-NEXT:       "file-deps": [
+// CHECK-NEXT:         "[[PREFIX]]/first/module.modulemap",
+// CHECK-NEXT:         "[[PREFIX]]/second/module.modulemap",
+// CHECK-NEXT:         "[[PREFIX]]/second/second.modulemap",
+// CHECK-NEXT:         "[[PREFIX]]/zeroth/module.modulemap",
+// CHECK-NEXT:         "[[PREFIX]]/zeroth/zeroth.h"
+// CHECK-NEXT:       ],
+// CHECK-NEXT:       "name": "zeroth"
+// CHECK-NEXT:     }
+// CHECK-NEXT:   ],
+// CHECK-NEXT:   "translation-units": [
+// CHECK-NEXT:     {
+// CHECK-NEXT:       "commands": [
+// CHECK-NEXT:         {
+// CHECK-NEXT:           "clang-context-hash": "{{.*}}",
+// CHECK-NEXT:           "clang-module-deps": [
+// CHECK-NEXT:             {
+// CHECK-NEXT:               "context-hash": "{{.*}}",
+// CHECK-NEXT:               "module-name": "zeroth"
+// CHECK-NEXT:             }
+// CHECK-NEXT:           ],
+// CHECK-NEXT:           "command-line": [
+// CHECK:                ],
+// CHECK-NEXT:           "executable": "clang",
+// CHECK-NEXT:           "file-deps": [
+// CHECK-NEXT:             "[[PREFIX]]/tu.m"
+// CHECK-NEXT:           ],
+// CHECK-NEXT:           "input-file": "[[PREFIX]]/tu.m"
+// CHECK-NEXT:         }
+// CHECK-NEXT:       ]
+// CHECK-NEXT:     }
+// CHECK-NEXT:   ]
+// CHECK-NEXT: }
+
+// RUN: %deps-to-rsp --module-name=first %t/result.json > %t/first.cc1.rsp
+// RUN: %deps-to-rsp --module-name=first_other %t/result.json > %t/first_other.cc1.rsp
+// RUN: %deps-to-rsp --module-name=second %t/result.json > %t/second.cc1.rsp
+// RUN: %deps-to-rsp --module-name=zeroth %t/result.json > %t/zeroth.cc1.rsp
+// RUN: %clang @%t/first.cc1.rsp
+// RUN: %clang @%t/first_other.cc1.rsp
+// RUN: %clang @%t/second.cc1.rsp
+// RUN: %clang @%t/zeroth.cc1.rsp