diff --git a/ghc/compiler/deSugar/DsCCall.lhs b/ghc/compiler/deSugar/DsCCall.lhs
index eab46af4e0c0a5c91e98de9c3d54919f65096c64..7e1bc0e3c20ed078881887006140429a220cafbb 100644
--- a/ghc/compiler/deSugar/DsCCall.lhs
+++ b/ghc/compiler/deSugar/DsCCall.lhs
@@ -156,7 +156,8 @@ unboxArg arg
     )
 
   | otherwise
-  = pprPanic "unboxArg: " (ppr arg_ty)
+  = getSrcLocDs `thenDs` \ l ->
+    pprPanic "unboxArg: " (ppr l <+> ppr arg_ty)
   where
     arg_ty = coreExprType arg