diff --git a/src/clang_complete.cc b/src/clang_complete.cc
index 18fc897d..97ad5c65 100644
--- a/src/clang_complete.cc
+++ b/src/clang_complete.cc
@@ -294,7 +294,8 @@ void EnsureDocumentParsed(ClangCompleteManager* manager,
     NonElidedVector<lsDiagnostic> ls_diagnostics;
     unsigned num_diagnostics = clang_getNumDiagnostics((*tu)->cx_tu);
     for (unsigned i = 0; i < num_diagnostics; ++i) {
-      optional<lsDiagnostic> diagnostic = BuildAndDisposeDiagnostic(clang_getDiagnostic((*tu)->cx_tu, i));
+      optional<lsDiagnostic> diagnostic = BuildAndDisposeDiagnostic(
+          clang_getDiagnostic((*tu)->cx_tu, i), session->file.filename);
       if (diagnostic)
         ls_diagnostics.push_back(*diagnostic);
     }
@@ -404,20 +405,18 @@ void CompletionQueryMain(ClangCompleteManager* completion_manager) {
       request->on_complete(ls_result, false /*is_cached_result*/);
       timer.ResetAndPrint("[complete] Running user-given completion func");
 
-      /*
       unsigned num_diagnostics = clang_codeCompleteGetNumDiagnostics(cx_results);
       NonElidedVector<lsDiagnostic> ls_diagnostics;
       std::cerr << "!! There are " + std::to_string(num_diagnostics) + " diagnostics to build\n";
       for (unsigned i = 0; i < num_diagnostics; ++i) {
         std::cerr << "!! Building diagnostic " + std::to_string(i) + "\n";
         CXDiagnostic cx_diag = clang_codeCompleteGetDiagnostic(cx_results, i);
-        optional<lsDiagnostic> diagnostic = BuildAndDisposeDiagnostic(cx_diag);
+        optional<lsDiagnostic> diagnostic = BuildAndDisposeDiagnostic(cx_diag, path);
         if (diagnostic)
           ls_diagnostics.push_back(*diagnostic);
       }
       completion_manager->on_diagnostic_(session->file.filename, ls_diagnostics);
       timer.ResetAndPrint("[complete] Build diagnostics");
-      */
     }
 
     // Make sure |ls_results| is destroyed before clearing |cx_results|.
diff --git a/src/clang_utils.cc b/src/clang_utils.cc
index 70aac896..cd3de430 100644
--- a/src/clang_utils.cc
+++ b/src/clang_utils.cc
@@ -21,22 +21,22 @@ lsRange GetLsRangeForFixIt(const CXSourceRange& range) {
 
 }  // namespace
 
-optional<lsDiagnostic> BuildAndDisposeDiagnostic(CXDiagnostic diagnostic) {
-  // Skip diagnostics in system headers.
-  CXSourceLocation diag_loc = clang_getDiagnosticLocation(diagnostic);
-  if (clang_equalLocations(diag_loc, clang_getNullLocation()) ||
-      clang_Location_isInSystemHeader(diag_loc)) {
+optional<lsDiagnostic> BuildAndDisposeDiagnostic(
+    CXDiagnostic diagnostic, const std::string& path) {
+  // Get diagnostic location.
+  CXFile file;
+  unsigned int line, column;
+  clang_getSpellingLocation(
+      clang_getDiagnosticLocation(diagnostic), &file, &line, &column, nullptr);
+
+  // Only report diagnostics in the same file. Using
+  // clang_Location_isInSystemHeader causes crashes for some reason.
+  if (path != FileName(file)) {
     clang_disposeDiagnostic(diagnostic);
     return nullopt;
   }
 
-  // Get db so we can attribute diagnostic to the right indexed file.
-  CXFile file;
-  unsigned int line, column;
-  clang_getSpellingLocation(diag_loc, &file, &line, &column, nullptr);
-
   // Build diagnostic.
-
   lsDiagnostic ls_diagnostic;
 
   // TODO: consider using clang_getDiagnosticRange
diff --git a/src/clang_utils.h b/src/clang_utils.h
index 5e3494ea..dcc2d87a 100644
--- a/src/clang_utils.h
+++ b/src/clang_utils.h
@@ -9,7 +9,8 @@
 
 using namespace std::experimental;
 
-optional<lsDiagnostic> BuildAndDisposeDiagnostic(CXDiagnostic diagnostic);
+optional<lsDiagnostic> BuildAndDisposeDiagnostic(
+    CXDiagnostic diagnostic, const std::string& path);
 
 // Returns the absolute path to |file|.
 std::string FileName(CXFile file);
diff --git a/src/indexer.cc b/src/indexer.cc
index 00daf3ab..c8ddc4c0 100644
--- a/src/indexer.cc
+++ b/src/indexer.cc
@@ -373,7 +373,7 @@ void diagnostic(CXClientData client_data,
 
   for (unsigned i = 0; i < clang_getNumDiagnosticsInSet(diagnostics); ++i) {
     CXDiagnostic diagnostic = clang_getDiagnosticInSet(diagnostics, i);
-    
+
     // Skip diagnostics in system headers.
     CXSourceLocation diag_loc = clang_getDiagnosticLocation(diagnostic);
     if (clang_Location_isInSystemHeader(diag_loc))
@@ -386,9 +386,10 @@ void diagnostic(CXClientData client_data,
     IndexFile* db = ConsumeFile(param, file);
     if (!db)
       continue;
-    
+
     // Build diagnostic.
-    optional<lsDiagnostic> ls_diagnostic = BuildAndDisposeDiagnostic(diagnostic);
+    optional<lsDiagnostic> ls_diagnostic =
+        BuildAndDisposeDiagnostic(diagnostic, db->path);
     if (ls_diagnostic)
       db->diagnostics_.push_back(*ls_diagnostic);
   }