diff --git a/clang-tools-extra/modularize/CoverageChecker.cpp b/clang-tools-extra/modularize/CoverageChecker.cpp
index b3c4227b6238..8549c0d4a6e3 100644
--- a/clang-tools-extra/modularize/CoverageChecker.cpp
+++ b/clang-tools-extra/modularize/CoverageChecker.cpp
@@ -370,12 +370,18 @@ bool CoverageChecker::collectFileSystemHeaders(StringRef IncludePath) {
     I.increment(EC)) {
     if (EC)
       return false;
-    std::string file(I->path());
+    //std::string file(I->path());
+    StringRef file(I->path());
     I->status(Status);
     sys::fs::file_type type = Status.type();
     // If the file is a directory, ignore the name (but still recurses).
     if (type == sys::fs::file_type::directory_file)
       continue;
+    // Assume directories or files starting with '.' are private and not to
+    // be considered.
+    if (file.startswith(".") || (file.find("\\.") != StringRef::npos)
+      || (file.find("/.") != StringRef::npos))
+      continue;
     // If the file does not have a common header extension, ignore it.
     if (!ModularizeUtilities::isHeader(file))
       continue;
diff --git a/clang-tools-extra/modularize/ModularizeUtilities.cpp b/clang-tools-extra/modularize/ModularizeUtilities.cpp
index 08c92fc90c0d..1db60185656a 100644
--- a/clang-tools-extra/modularize/ModularizeUtilities.cpp
+++ b/clang-tools-extra/modularize/ModularizeUtilities.cpp
@@ -468,7 +468,7 @@ std::string ModularizeUtilities::getCanonicalPath(StringRef FilePath) {
 bool ModularizeUtilities::isHeader(StringRef FileName) {
   StringRef Extension = llvm::sys::path::extension(FileName);
   if (Extension.size() == 0)
-    return false;
+    return true;
   if (Extension.equals_lower(".h"))
     return true;
   if (Extension.equals_lower(".inc"))
diff --git a/clang-tools-extra/test/modularize/Inputs/CoverageNoProblems/Includes1/.hidden/DontFindMe.h b/clang-tools-extra/test/modularize/Inputs/CoverageNoProblems/Includes1/.hidden/DontFindMe.h
new file mode 100644
index 000000000000..f60b66cd1f62
--- /dev/null
+++ b/clang-tools-extra/test/modularize/Inputs/CoverageNoProblems/Includes1/.hidden/DontFindMe.h
@@ -0,0 +1,3 @@
+#error DontFindMe.h shouldn't be found.
+
+
diff --git a/clang-tools-extra/test/modularize/Inputs/CoverageProblems/Level3B b/clang-tools-extra/test/modularize/Inputs/CoverageProblems/Level3B
new file mode 100644
index 000000000000..e1eee7ef8b56
--- /dev/null
+++ b/clang-tools-extra/test/modularize/Inputs/CoverageProblems/Level3B
@@ -0,0 +1 @@
+#define MACRO_3B 1
diff --git a/clang-tools-extra/test/modularize/ProblemsCoverage.modularize b/clang-tools-extra/test/modularize/ProblemsCoverage.modularize
index 68224e1c3743..5a1c3489beb7 100644
--- a/clang-tools-extra/test/modularize/ProblemsCoverage.modularize
+++ b/clang-tools-extra/test/modularize/ProblemsCoverage.modularize
@@ -1,4 +1,5 @@
 # RUN: not modularize %S/Inputs/CoverageProblems/module.modulemap 2>&1 | FileCheck %s
 
 # CHECK: warning: {{.*}}{{[/\\]}}Inputs/CoverageProblems/module.modulemap does not account for file: {{.*}}{{[/\\]}}Inputs/CoverageProblems/Level3A.h
+# CHECK-NEXT: warning: {{.*}}{{[/\\]}}Inputs/CoverageProblems/module.modulemap does not account for file: {{.*}}{{[/\\]}}Inputs/CoverageProblems/Level3B
 # CHECK-NEXT: warning: {{.*}}{{[/\\]}}Inputs/CoverageProblems/module.modulemap does not account for file: {{.*}}{{[/\\]}}Inputs/CoverageProblems/Sub/Level3B.h