Using RMySQL interferes with RPostgreSQL - mysql

Question

I have an R script where I want to pull some data from a MySQL database, then from a PostgreSQL database. However, loading the MySQL driver from RMySQL prevents me from loading the PostgreSQL driver from PostgreSQL.
I can load the Postgres driver fine on its own:
> RPostgreSQL::PostgreSQL()
<PostgreSQLDriver:(58810)>
Then I can load the RMySQL driver:
> RMySQL::MySQL()
<MySQLDriver>
However, if I load the MySQL driver first, the PostgreSQL driver fails to load:
> RMySQL::MySQL()
<MySQLDriver>
> RPostgreSQL::PostgreSQL()
Error in as.integer(from) :
cannot coerce type 'S4' to vector of type 'integer'
This seems a little magical to me: RMySQL shouldn't be altering functions in RPostgreSQL's namespace.
Does anyone have any idea what might be causing this problem and how I can solve it? I've replicated the problem on 2 different machines, with the exact same results.
Machine 1: Mac OS 10.9.5:
Machine R version 3.1.2 (2014-10-31)
Platform: x86_64-apple-darwin13.4.0 (64-bit)
locale:
[1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] DBI_0.3.1 RMySQL_0.10 RPostgreSQL_0.41
Machine 2: Fedora release 20 (Heisenbug):
R version 3.1.1 (2014-07-10)
Platform: x86_64-redhat-linux-gnu (64-bit)
locale:
[1] LC_CTYPE=en_US.UTF-8 LC_NUMERIC=C
[3] LC_TIME=en_US.UTF-8 LC_COLLATE=en_US.UTF-8
[5] LC_MONETARY=en_US.UTF-8 LC_MESSAGES=en_US.UTF-8
[7] LC_PAPER=en_US.UTF-8 LC_NAME=C
[9] LC_ADDRESS=C LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_US.UTF-8 LC_IDENTIFICATION=C
attached base packages:
[1] stats graphics grDevices utils datasets methods base
loaded via a namespace (and not attached):
[1] DBI_0.3.1 RMySQL_0.10 RPostgreSQL_0.4
/edit: Furthermore, even if I load the Postgres driver first, merely loading the MySQL driver completely borks the Postgres driver:
library(DBI)
dr1 <- RPostgreSQL::PostgreSQL()
dr2 <- RMySQL::MySQL()
> dbConnect(dr1, host = "me", port = "1234", dbname = "me", user="me", password="me")
Error in as.integer(from) :
cannot coerce type 'S4' to vector of type 'integer'
/edit 2: This is a bug in RMySQL 0.10; the above code works fine in RMySQL 0.9.3. Judging from this 20-month old question, a similar bug crops up from time to time in RMySQL.