diff --git a/R/pkg/R/mllib_classification.R b/R/pkg/R/mllib_classification.R
index 093467ecf7d28..7204f8bb7dff4 100644
--- a/R/pkg/R/mllib_classification.R
+++ b/R/pkg/R/mllib_classification.R
@@ -322,7 +322,7 @@ setMethod("spark.logit", signature(data = "SparkDataFrame", formula = "formula")
             }
 
             if (!is.null(lowerBoundsOnCoefficients)) {
-              if (class(lowerBoundsOnCoefficients) != "matrix") {
+              if (!is.matrix(lowerBoundsOnCoefficients)) {
                 stop("lowerBoundsOnCoefficients must be a matrix.")
               }
               row <- nrow(lowerBoundsOnCoefficients)
@@ -331,7 +331,7 @@ setMethod("spark.logit", signature(data = "SparkDataFrame", formula = "formula")
             }
 
             if (!is.null(upperBoundsOnCoefficients)) {
-              if (class(upperBoundsOnCoefficients) != "matrix") {
+              if (!is.matrix(upperBoundsOnCoefficients)) {
                 stop("upperBoundsOnCoefficients must be a matrix.")
               }
 
diff --git a/R/pkg/R/serialize.R b/R/pkg/R/serialize.R
index 7760d9be16f0b..85c318f30c338 100644
--- a/R/pkg/R/serialize.R
+++ b/R/pkg/R/serialize.R
@@ -58,7 +58,12 @@ writeObject <- function(con, object, writeType = TRUE) {
   # Checking types is needed here, since 'is.na' only handles atomic vectors,
   # lists and pairlists
   if (type %in% c("integer", "character", "logical", "double", "numeric")) {
-    if (is.na(object)) {
+    if (is.na(object[[1]])) {
+      # Uses the first element for now to keep the behavior same as R before
+      # 4.2.0. This is wrong because we should differenciate c(NA) from a
+      # single NA as the former means array(null) and the latter means null
+      # in Spark SQL. However, it requires non-trivial comparison to distinguish
+      # both in R. We should ideally fix this.
       object <- NULL
       type <- "NULL"
     }
diff --git a/dev/appveyor-install-dependencies.ps1 b/dev/appveyor-install-dependencies.ps1
index d469c98fdb3a2..19b49b90b3859 100644
--- a/dev/appveyor-install-dependencies.ps1
+++ b/dev/appveyor-install-dependencies.ps1
@@ -129,7 +129,7 @@ $env:PATH = "$env:HADOOP_HOME\bin;" + $env:PATH
 Pop-Location
 
 # ========================== R
-$rVer = "4.0.2"
+$rVer = "4.2.0"
 $rToolsVer = "4.0.2"
 
 InstallR