diff --git a/external/cosmotool/src/yorick_nc3.cpp b/external/cosmotool/src/yorick_nc3.cpp
index d760009..92d55b6 100644
--- a/external/cosmotool/src/yorick_nc3.cpp
+++ b/external/cosmotool/src/yorick_nc3.cpp
@@ -151,7 +151,7 @@ namespace CosmoTool {
   ProgressiveOutput<T>::saveArrayProgressive(const std::string& fname, uint32_t *dimList,
 					     uint32_t rank)
   {
-    NcFile *f = new NcFile(fname.c_str(), NcFile::Replace);
+    NcFile *f = new NcFile(fname.c_str(), NcFile::Replace, 0, 0, NcFile::Netcdf4);
     
     assert(f->is_valid());
     
@@ -202,7 +202,7 @@ namespace CosmoTool {
   void saveArray(const std::string& fname,
 		 T *array, uint32_t *dimList, uint32_t rank)
   {
-    NcFile f(fname.c_str(), NcFile::Replace);
+    NcFile f(fname.c_str(), NcFile::Replace, 0, 0, NcFile::Netcdf4);
     
     assert(f.is_valid());