diff --git a/plugins/clang/duchain/parsesession.cpp b/plugins/clang/duchain/parsesession.cpp
--- a/plugins/clang/duchain/parsesession.cpp
+++ b/plugins/clang/duchain/parsesession.cpp
@@ -145,7 +145,7 @@
         if (url.isEmpty()) {
             continue;
         }
-        
+
         QFileInfo info(url.toLocalFile());
         QByteArray path = url.toLocalFile().toUtf8();
 
@@ -280,6 +280,9 @@
     smartArgs << writeDefinesFile(environment.defines());
     clangArguments << "-imacros" << smartArgs.last().constData();
 
+#ifdef __FreeBSD__
+    clangArguments << "-isystem" << "/usr/include";
+#endif
     // append extra args from environment variable
     static const auto extraArgs = ::extraArgs();
     foreach (const QByteArray& arg, extraArgs) {
diff --git a/plugins/custom-definesandincludes/compilerprovider/gcclikecompiler.cpp b/plugins/custom-definesandincludes/compilerprovider/gcclikecompiler.cpp
--- a/plugins/custom-definesandincludes/compilerprovider/gcclikecompiler.cpp
+++ b/plugins/custom-definesandincludes/compilerprovider/gcclikecompiler.cpp
@@ -191,7 +191,7 @@
                     // This is an include path, add it to the list.
                     auto hostPath = rt->pathInHost(Path(line.trimmed().toString()));
                     // but skip folders with compiler builtins, we cannot parse these with clang
-                    if (!QFile::exists(hostPath.toLocalFile() + QLatin1String("/varargs.h"))) {
+                    if (!QFile::exists(hostPath.toLocalFile() + QLatin1String("/vadefs.h"))) {
                         data.includePaths << Path(QFileInfo(hostPath.toLocalFile()).canonicalFilePath());
                     }
                 }