Accessing tables in non-default schemas in PostgreSQL

I have a problem with PostgreSQL connection and R; when I run

dbWriteTable(con, in_schema('my_schema', 'my_table'), my_data_frame, append = T) 

it creates a new table named public."my_schema.my_table" in the default schema, instead of appending rows to existing (and expected) table my_schema.my_table.

I can work around the issue (via running SQL code to insert data from the wrong table to the correct one), but it is rather annoying. Is there another way to specify schemas, or to handle quotation marks? I suspect that my issue relates to the way quotations are handled, though I am not 100% sure.

I am running R 3.5.1 with DBI 1.0.0, dbplyr 1.2.2 and odbc 1.1.6; driver is PostgreSQL Unicode.