Index: clang-tidy/ClangTidyDiagnosticConsumer.cpp
===================================================================
--- clang-tidy/ClangTidyDiagnosticConsumer.cpp
+++ clang-tidy/ClangTidyDiagnosticConsumer.cpp
@@ -239,7 +239,10 @@
   if (FID == Sources.getMainFileID())
     return true;
 
-  return HeaderFilter.match(Sources.getFileEntryForID(FID)->getName());
+  const FileEntry *File = Sources.getFileEntryForID(FID);
+  // -DMACRO definitions on the command line have locations in a virtual buffer
+  // that doesn't have a FileEntry. Don't skip these as well.
+  return !File || HeaderFilter.match(File->getName());
 }
 
 struct LessClangTidyError {
Index: test/clang-tidy/diagnostic.cpp
===================================================================
--- test/clang-tidy/diagnostic.cpp
+++ test/clang-tidy/diagnostic.cpp
@@ -1,6 +1,7 @@
 // RUN: clang-tidy -disable-checks='' %s.nonexistent.cpp -- | FileCheck -check-prefix=CHECK1 %s
 // RUN: clang-tidy -disable-checks='' %s -- -fan-unknown-option | FileCheck -check-prefix=CHECK2 %s
 // RUN: clang-tidy -checks='(google-explicit-constructor|clang-diagnostic-literal-conversion)' -disable-checks='' %s -- -fan-unknown-option | FileCheck -check-prefix=CHECK3 %s
+// RUN: clang-tidy -checks='clang-diagnostic-macro-redefined' -disable-checks='' %s -- -DMACRO_FROM_COMMAND_LINE | FileCheck -check-prefix=CHECK4 %s
 
 // CHECK1-NOT: warning
 // CHECK2-NOT: warning
@@ -19,3 +20,6 @@
 
 // CHECK2-NOT: warning:
 // CHECK3-NOT: warning:
+
+#define MACRO_FROM_COMMAND_LINE
+// CHECK4: :[[@LINE-1]]:9: warning: 'MACRO_FROM_COMMAND_LINE' macro redefined