diff --git a/clang/lib/Tooling/DependencyScanning/DependencyScanningFilesystem.cpp b/clang/lib/Tooling/DependencyScanning/DependencyScanningFilesystem.cpp
--- a/clang/lib/Tooling/DependencyScanning/DependencyScanningFilesystem.cpp
+++ b/clang/lib/Tooling/DependencyScanning/DependencyScanningFilesystem.cpp
@@ -122,6 +122,32 @@
   return It.first->getValue();
 }
 
+/// Whitelist file extensions that should be minimized, treating no extension as
+/// a source file that should be minimized.
+///
+/// This is kinda hacky, it would be better if we knew what kind of file Clang
+/// was expecting instead.
+static bool shouldMinimize(StringRef Filename) {
+  StringRef Ext = llvm::sys::path::extension(Filename);
+  if (Ext.empty())
+    return true; // C++ standard library
+  return llvm::StringSwitch<bool>(Ext)
+    .CasesLower(".c", ".cc", ".cpp", ".c++", ".cxx", true)
+    .CasesLower(".h", ".hh", ".hpp", ".h++", ".hxx", true)
+    .CasesLower(".m", ".mm", true)
+    .CasesLower(".i", ".ii", ".mi", ".mmi", true)
+    .CasesLower(".def", ".inc", true)
+    .Default(false);
+}
+
+
+static bool shouldCacheStatFailures(StringRef Filename) {
+  StringRef Ext = llvm::sys::path::extension(Filename);
+  if (Ext.empty())
+    return false; // This may be the module cache directory.
+  return shouldMinimize(Filename); // Only cache stat failures on source files.
+}
+
 llvm::ErrorOr<const CachedFileSystemEntry *>
 DependencyScanningWorkerFilesystem::getOrCreateFileSystemEntry(
     const StringRef Filename) {
@@ -132,7 +158,8 @@
   // FIXME: Handle PCM/PCH files.
   // FIXME: Handle module map files.
 
-  bool KeepOriginalSource = IgnoredFiles.count(Filename);
+  bool KeepOriginalSource = IgnoredFiles.count(Filename) ||
+                            !shouldMinimize(Filename);
   DependencyScanningFilesystemSharedCache::SharedFileSystemEntry
       &SharedCacheEntry = SharedCache.get(Filename);
   const CachedFileSystemEntry *Result;
@@ -143,9 +170,16 @@
     if (!CacheEntry.isValid()) {
       llvm::vfs::FileSystem &FS = getUnderlyingFS();
       auto MaybeStatus = FS.status(Filename);
-      if (!MaybeStatus)
-        CacheEntry = CachedFileSystemEntry(MaybeStatus.getError());
-      else if (MaybeStatus->isDirectory())
+      if (!MaybeStatus) {
+        if (!shouldCacheStatFailures(Filename))
+          // HACK: We need to always restat non source files if the stat fails.
+          //   This is because Clang first looks up the module cache and module
+          //   files before building them, and then looks for them again. If we
+          //   cache the stat failure, it won't see them the second time.
+          return MaybeStatus.getError();
+        else
+          CacheEntry = CachedFileSystemEntry(MaybeStatus.getError());
+      } else if (MaybeStatus->isDirectory())
         CacheEntry = CachedFileSystemEntry::createDirectoryEntry(
             std::move(*MaybeStatus));
       else
diff --git a/clang/test/ClangScanDeps/Inputs/module.modulemap b/clang/test/ClangScanDeps/Inputs/module.modulemap
new file mode 100644
--- /dev/null
+++ b/clang/test/ClangScanDeps/Inputs/module.modulemap
@@ -0,0 +1,7 @@
+module header1 {
+  header "header.h"
+}
+
+module header2 {
+    header "header2.h"
+}
diff --git a/clang/test/ClangScanDeps/Inputs/modules_cdb.json b/clang/test/ClangScanDeps/Inputs/modules_cdb.json
new file mode 100644
--- /dev/null
+++ b/clang/test/ClangScanDeps/Inputs/modules_cdb.json
@@ -0,0 +1,13 @@
+[
+{
+  "directory": "DIR",
+  "command": "clang -E -fsyntax-only DIR/modules_cdb_input2.cpp -IInputs -D INCLUDE_HEADER2 -MD -MF DIR/modules_cdb2.d -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fimplicit-module-maps",
+  "file": "DIR/modules_cdb_input2.cpp"
+},
+{
+  "directory": "DIR",
+  "command": "clang -E DIR/modules_cdb_input.cpp -IInputs -fmodules -fmodules-cache-path=DIR/module-cache -fimplicit-modules -fimplicit-module-maps",
+  "file": "DIR/modules_cdb_input.cpp"
+}
+]
+
diff --git a/clang/test/ClangScanDeps/modules.cpp b/clang/test/ClangScanDeps/modules.cpp
new file mode 100644
--- /dev/null
+++ b/clang/test/ClangScanDeps/modules.cpp
@@ -0,0 +1,41 @@
+// RUN: rm -rf %t.dir
+// RUN: rm -rf %t.cdb
+// RUN: rm -rf %t.module-cache
+// RUN: mkdir -p %t.dir
+// RUN: cp %s %t.dir/modules_cdb_input.cpp
+// RUN: cp %s %t.dir/modules_cdb_input2.cpp
+// RUN: mkdir %t.dir/Inputs
+// RUN: cp %S/Inputs/header.h %t.dir/Inputs/header.h
+// RUN: cp %S/Inputs/header2.h %t.dir/Inputs/header2.h
+// RUN: cp %S/Inputs/module.modulemap %t.dir/Inputs/module.modulemap
+// RUN: sed -e "s|DIR|%/t.dir|g" %S/Inputs/modules_cdb.json > %t.cdb
+//
+// RUN: clang-scan-deps -compilation-database %t.cdb -j 1 -mode preprocess-minimized-sources | \
+// RUN:   FileCheck --check-prefixes=CHECK1,CHECK2,CHECK2NO %s
+//
+// The output order is non-deterministic when using more than one thread,
+// so check the output using two runs. Note that the 'NOT' check is not used
+// as it might fail if the results for `modules_cdb_input.cpp` are reported before
+// `modules_cdb_input2.cpp`.
+//
+// RUN: clang-scan-deps -compilation-database %t.cdb -j 2 -mode preprocess-minimized-sources | \
+// RUN:   FileCheck --check-prefix=CHECK1 %s
+// RUN: clang-scan-deps -compilation-database %t.cdb -j 2 -mode preprocess | \
+// RUN:   FileCheck --check-prefix=CHECK1 %s
+// RUN: clang-scan-deps -compilation-database %t.cdb -j 2 -mode preprocess-minimized-sources | \
+// RUN:   FileCheck --check-prefix=CHECK2 %s
+// RUN: clang-scan-deps -compilation-database %t.cdb -j 2 -mode preprocess | \
+// RUN:   FileCheck --check-prefix=CHECK2 %s
+
+#include "header.h"
+
+// CHECK1: modules_cdb_input2.cpp
+// CHECK1-NEXT: modules_cdb_input2.cpp
+// CHECK1-NEXT: Inputs{{/|\\}}module.modulemap
+// CHECK1-NEXT: Inputs{{/|\\}}header2.h
+// CHECK1: Inputs{{/|\\}}header.h
+
+// CHECK2: modules_cdb_input.cpp
+// CHECK2-NEXT: Inputs{{/|\\}}module.modulemap
+// CHECK2-NEXT: Inputs{{/|\\}}header.h
+// CHECK2NO-NOT: header2