diff --git a/clang/lib/Analysis/FormatString.cpp b/clang/lib/Analysis/FormatString.cpp
index 5785655..dd2f240 100644
--- a/clang/lib/Analysis/FormatString.cpp
+++ b/clang/lib/Analysis/FormatString.cpp
@@ -156,6 +156,9 @@
   }
 
   if (Amt.getHowSpecified() == OptionalAmount::Constant && *(I++) == '$') {
+    // Warn that positional arguments are non-standard.
+    H.HandlePosition(Start, I - Start);
+
     // Special case: '%0$', since this is an easy mistake.
     if (Amt.getConstantAmount() == 0) {
       H.HandleZeroPosition(Start, I - Start);