Fix compilation

diff --git a/source/base/data_out_base.cc b/source/base/data_out_base.cc
index cfdf5227d8c7c0736600facea0c9c75ed5f1857f..295babfe601eea53fcd5a73fb522651d9a9485d5 100644 (file)
--- a/source/base/data_out_base.cc
+++ b/source/base/data_out_base.cc
@@ -9070,7 +9070,7 @@ namespace DataOutBase
     }
 
     // First import what kind of reference cell we are looking at:
-#if DEAL_II_HAVE_CXX17
+#ifdef DEAL_II_HAVE_CXX17
     if constexpr (dim > 0)
       in >> patch.reference_cell;
 #else