diff --git a/ocean_data_tools/wod_build.m b/ocean_data_tools/wod_build.m
index 696af2a..89cface 100644
--- a/ocean_data_tools/wod_build.m
+++ b/ocean_data_tools/wod_build.m
@@ -82,7 +82,7 @@
     is_matrix = sz1(1,:)~=1;
 
     % load data into structured array
-    wod.stn = NaN(1,prof_dim);
+    wod.stn = 1:prof_dim;
     for var = 1:var_dim
         variable = variable_list{var};
         if is_matrix(var)