diff --git a/src/trexio/export_trexio_routines.irp.f b/src/trexio/export_trexio_routines.irp.f
index 53b21dc9..0c70b5e6 100644
--- a/src/trexio/export_trexio_routines.irp.f
+++ b/src/trexio/export_trexio_routines.irp.f
@@ -72,7 +72,7 @@ subroutine export_trexio(update,full_path)
   character*(64) :: code(100), author(100), user
   character*(64), parameter :: qp2_code = "QuantumPackage"
 
-  call getenv("USER",user)
+  call getenv('USER',user)
   do k=1,N_states
     rc = trexio_read_metadata_code_num(f(k), code_num)
     if (rc == TREXIO_ATTR_MISSING) then
@@ -95,25 +95,27 @@ subroutine export_trexio(update,full_path)
       call trexio_assert(rc, TREXIO_SUCCESS)
     endif
 
-    rc = trexio_read_metadata_author_num(f(k), author_num)
-    if (rc == TREXIO_ATTR_MISSING) then
-      i = 1
-      author_num = 0
-      author(:) = ""
-    else
-      rc = trexio_read_metadata_author(f(k), author, 64)
-      do i=1, author_num
-        if (trim(author(i)) == trim(user)) then
-          exit
-        endif
-      enddo
-    endif
-    if (i == author_num+1) then
-      author(i) = user
-      rc = trexio_write_metadata_author_num(f(k), i)
-      call trexio_assert(rc, TREXIO_SUCCESS)
-      rc = trexio_write_metadata_author(f(k), author, 64)
-      call trexio_assert(rc, TREXIO_SUCCESS)
+    if (trim(user) /= '') then
+      rc = trexio_read_metadata_author_num(f(k), author_num)
+      if (rc == TREXIO_ATTR_MISSING) then
+        i = 1
+        author_num = 0
+        author(:) = ""
+      else
+        rc = trexio_read_metadata_author(f(k), author, 64)
+        do i=1, author_num
+          if (trim(author(i)) == trim(user)) then
+            exit
+          endif
+        enddo
+      endif
+      if (i == author_num+1) then
+        author(i) = user
+        rc = trexio_write_metadata_author_num(f(k), i)
+        call trexio_assert(rc, TREXIO_SUCCESS)
+        rc = trexio_write_metadata_author(f(k), author, 64)
+        call trexio_assert(rc, TREXIO_SUCCESS)
+      endif
     endif
   enddo