openxlsx::write.xlsx throwing unused argument error for startRow - r

Question

I want to read a bunch of excel files all located in the same directory and store them in different sheets in a consolidated Excel file.
I am using a combination of xlsx and openxlsx to achieve this. The reason is, openxlsx can not read .xls file and xlsx is java based and runs out of memory throwing GC overhead limit exceeded error when trying to write large files.
Here is the code I am using:
library(openxlsx)
library(xlsx)
mnth="january"
outputFileName<-"Consolidated.xlsx"
files <- list.files(path="./Original Files", pattern=mnth, full.names=T, recursive=FALSE)
start_row<-1
lapply(files, function(x){
print(x)
xlFile<-read.xlsx2(x, sheetIndex = 1, startRow = 2, header =T) #Reads all columns as factors
#Write to Excel
write.xlsx(xlFile, file=outputFileName, sheetName = mnth, startRow = start_row)
start_row<- start_row + nrow(xlFile)
})
I am trying to read all the files with January (Ex: january2015, january 2016) and append the rows in the same sheet of a Consolidated xlsx file.
However I am getting the error:
Error in write.xlsx(xlFile, file = outputFileName, sheetName = mnth, :
unused argument (startRow = start_row)
The documentation clearly mentions that startRow is an optional parameter. Interestingly, sheetName is also an optional parameter but does not throw errors.
I have ran the code with startRow = start_row removed and it works as expected, i.e., the contents are repeatedly overwritten with only the contents of the last xls file prevailing.
UPDATE
I have changed the reading function from functions from XLConnect to avoid having the several functions with similar names, and I still get the same error:
Error in write.xlsx(xlFile, file = outputFileName, sheetName = placename, :
unused argument (startRow = start_row)
Here is the code with XLConnect:
lapply(files, function(x){
print(x)
xlFile<-readWorksheetFromFile(file = x, sheet=1, startRow=2)
str(xlFile)
l=list(dt,xlFile)
#Write to Excel
write.xlsx(xlFile, file=outputFileName, sheetName = mnth, startRow = start_row)
start_row<- start_row + nrow(xlFile)
})