diff --git a/clang/include/clang/Basic/LangOptions.h b/clang/include/clang/Basic/LangOptions.h
--- a/clang/include/clang/Basic/LangOptions.h
+++ b/clang/include/clang/Basic/LangOptions.h
@@ -505,6 +505,11 @@
     return getCompilingModule() == CMK_ModuleInterface;
   }
 
+  /// Are we compiling a module implementation?
+  bool isCompilingModuleImplementation() const {
+    return !isCompilingModule() && !ModuleName.empty();
+  }
+
   /// Do we need to track the owning module for a local declaration?
   bool trackLocalOwningModule() const {
     return isCompilingModule() || ModulesLocalVisibility;
diff --git a/clang/include/clang/Lex/Preprocessor.h b/clang/include/clang/Lex/Preprocessor.h
--- a/clang/include/clang/Lex/Preprocessor.h
+++ b/clang/include/clang/Lex/Preprocessor.h
@@ -2231,6 +2231,9 @@
   /// Retrieves the module that we're currently building, if any.
   Module *getCurrentModule();
 
+  /// Retrieves the module whose implementation we're current compiling, if any.
+  Module *getCurrentModuleImplementation();
+
   /// Allocate a new MacroInfo object with the provided SourceLocation.
   MacroInfo *AllocateMacroInfo(SourceLocation L);
 
diff --git a/clang/lib/Lex/Preprocessor.cpp b/clang/lib/Lex/Preprocessor.cpp
--- a/clang/lib/Lex/Preprocessor.cpp
+++ b/clang/lib/Lex/Preprocessor.cpp
@@ -534,6 +534,13 @@
   return getHeaderSearchInfo().lookupModule(getLangOpts().CurrentModule);
 }
 
+Module *Preprocessor::getCurrentModuleImplementation() {
+  if (!getLangOpts().isCompilingModuleImplementation())
+    return nullptr;
+
+  return getHeaderSearchInfo().lookupModule(getLangOpts().ModuleName);
+}
+
 //===----------------------------------------------------------------------===//
 // Preprocessor Initialization Methods
 //===----------------------------------------------------------------------===//
diff --git a/clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp b/clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
--- a/clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
+++ b/clang/lib/Tooling/DependencyScanning/ModuleDepCollector.cpp
@@ -188,6 +188,14 @@
 void ModuleDepCollector::applyDiscoveredDependencies(CompilerInvocation &CI) {
   CI.clearImplicitModuleBuildOptions();
 
+  Preprocessor &PP = ScanInstance.getPreprocessor();
+  if (Module *CurrentModule = PP.getCurrentModuleImplementation()) {
+    const FileEntry *CurrentModMap =
+        PP.getHeaderSearchInfo().getModuleMap().getModuleMapFileForUniquing(
+            CurrentModule);
+    CI.getFrontendOpts().ModuleMapFiles.emplace_back(CurrentModMap->getName());
+  }
+
   if (llvm::any_of(CI.getFrontendOpts().Inputs, needsModules)) {
     SmallVector<ModuleID> DirectDeps;
     for (const auto &KV : ModularDeps)
diff --git a/clang/test/ClangScanDeps/modules-header-sharing.m b/clang/test/ClangScanDeps/modules-header-sharing.m
new file mode 100644
--- /dev/null
+++ b/clang/test/ClangScanDeps/modules-header-sharing.m
@@ -0,0 +1,96 @@
+// There are some edge-cases where Clang depends on knowing the module whose implementation it's currently building.
+// This test makes sure scanner always reports the corresponding module map.
+
+// RUN: rm -rf %t
+// RUN: split-file %s %t
+
+//--- frameworks/A.framework/Modules/module.modulemap
+framework module A { umbrella header "A.h" }
+//--- frameworks/B.framework/Modules/module.modulemap
+framework module B { umbrella header "B.h" }
+//--- frameworks/A.framework/Headers/A.h
+//--- frameworks/B.framework/Headers/B.h
+//--- frameworks/A.framework/Modules/module.private.modulemap
+framework module A_Private { umbrella header "A_Private.h" }
+//--- frameworks/B.framework/Modules/module.private.modulemap
+framework module B_Private { umbrella header "B_Private.h" }
+//--- frameworks/A.framework/PrivateHeaders/A_Private.h
+#import <A/H.h>
+//--- frameworks/B.framework/PrivateHeaders/B_Private.h
+#import <B/H.h>
+
+//--- shared/H.h
+
+//--- overlay.json.template
+{
+  "case-sensitive": "false",
+  "version": 0,
+  "roots": [
+    {
+      "contents": [
+        {
+          "external-contents": "DIR/shared/H.h",
+          "name": "H.h",
+          "type": "file"
+        }
+      ],
+      "name": "DIR/frameworks/A.framework/PrivateHeaders",
+      "type": "directory"
+    },
+    {
+      "contents": [
+        {
+          "external-contents": "DIR/shared/H.h",
+          "name": "H.h",
+          "type": "file"
+        }
+      ],
+      "name": "DIR/frameworks/B.framework/PrivateHeaders",
+      "type": "directory"
+    }
+  ]
+}
+
+//--- cdb.json.template
+[{
+  "file": "DIR/tu.m",
+  "directory": "DIR",
+  "command": "clang -fmodules -fmodules-cache-path=DIR/cache -fmodule-name=A -ivfsoverlay DIR/overlay.json -F DIR/frameworks -c DIR/tu.m -o DIR/tu.o"
+}]
+
+//--- tu.m
+@import B;
+#import <A/H.h>
+#import <B/H.h>
+
+// RUN: sed -e "s|DIR|%/t|g" %t/cdb.json.template > %t/cdb.json
+// RUN: sed -e "s|DIR|%/t|g" %t/overlay.json.template > %t/overlay.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:        "translation-units": [
+// CHECK-NEXT:     {
+// CHECK-NEXT:       "commands": [
+// CHECK-NEXT:         {
+// CHECK:                "command-line": [
+// CHECK:                  "-fmodule-map-file=[[PREFIX]]/frameworks/A.framework/Modules/module.modulemap",
+// CHECK:                  "-fmodule-name=A",
+// CHECK:                ],
+// CHECK-NEXT:           "executable": "clang",
+// CHECK-NEXT:           "file-deps": [
+// CHECK-NEXT:             "[[PREFIX]]/tu.m",
+// CHECK-NEXT:             "[[PREFIX]]/shared/H.h"
+// CHECK-NEXT:           ],
+// CHECK-NEXT:           "input-file": "[[PREFIX]]/tu.m"
+// CHECK-NEXT:         }
+// CHECK-NEXT:       ]
+// CHECK-NEXT:     }
+// CHECK-NEXT:   ]
+// CHECK-NEXT: }
+
+// RUN: %deps-to-rsp %t/result.json --module-name=B > %t/B.cc1.rsp
+// RUN: %clang @%t/B.cc1.rsp
+
+// RUN: %deps-to-rsp %t/result.json --tu-index=0 > %t/tu.rsp
+// RUN: %clang @%t/tu.rsp