diff --git a/test/Preprocessor/undef-error.c b/test/Preprocessor/undef-error.c
new file mode 100644
index 0000000..af9f516
--- /dev/null
+++ b/test/Preprocessor/undef-error.c
@@ -0,0 +1,5 @@
+// RUN: not clang %s -pedantic-errors -E
+// PR2045
+
+#define b
+#undef a b