diff --git a/src/fix.cpp b/src/fix.cpp
index fc9786d060..2a794fe8ae 100644
--- a/src/fix.cpp
+++ b/src/fix.cpp
@@ -70,13 +70,17 @@ Fix::Fix(LAMMPS *lmp, int narg, char **arg) : Pointers(lmp)
   // however, each fix that uses these values should explicitly set them
 
   nevery = 1;
-  
 
   maxvatom = 0;
   vatom = NULL;
 
+  // CUDA and KOKKOS per-fix data masks
+
   datamask = ALL_MASK;
   datamask_ext = ALL_MASK;
+
+  datamask_read = datamask_read_ext = ALL_MASK;
+  datamask_modify = datamask_modify_ext = ALL_MASK;
 }
 
 /* ---------------------------------------------------------------------- */