diff --git a/NAMESPACE b/NAMESPACE
index 0cb344b..b1a4467 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -109,7 +109,6 @@ importFrom(plyr,compact)
 importFrom(plyr,ddply)
 importFrom(plyr,desc)
 importFrom(plyr,dlply)
-importFrom(plyr,is.discrete)
 importFrom(plyr,is.formula)
 importFrom(plyr,join)
 importFrom(plyr,ldply)
diff --git a/R/ggmap-package.R b/R/ggmap-package.R
index 7b05f38..22139fc 100644
--- a/R/ggmap-package.R
+++ b/R/ggmap-package.R
@@ -2,7 +2,7 @@
 #' @name ggmap
 #' @importFrom png readPNG
 #' @importFrom jpeg readJPEG
-#' @importFrom plyr arrange compact ddply desc dlply is.discrete is.formula join
+#' @importFrom plyr arrange compact ddply desc dlply is.formula join
 #'   ldply llply .
 #' @importFrom bitops bitOr bitShiftL bitShiftR bitAnd
 #' @importFrom grDevices as.raster extendrange gray rgb
diff --git a/R/qmplot.R b/R/qmplot.R
index b2af1d4..74dcb98 100644
--- a/R/qmplot.R
+++ b/R/qmplot.R
@@ -299,7 +299,7 @@ qmplot <- function(x, y, ..., data, zoom, source = "stadia", maptype = "stamen_t
       geom[geom == "auto"] <- "qq"
     } else if (missing(y)) {
       x <- eval(aesthetics$x, data, env)
-      if (is.discrete(x)) {
+      if (is.factor(x) || is.character(x) || is.logical(x)) {
         geom[geom == "auto"] <- "bar"
       } else {
         geom[geom == "auto"] <- "histogram"