RPostgresql executing a function that returns void

Question

I have a code that looks like this:

con <- connect_to_my_postgres_database()

dbClearResult(dbExecute(con, "select function_that_returns_void()")

postgresqlCloseConnection(con)

This is yielding the error:

Condition: RPosgreSQL warning: unrecognized PostgreSQL field type void (id:2278) in column 0
NULL
Error in postgresqlCloseConnection(con) :
  connection has pending rows (close open results set first)
Execution halted

How to fix this error?