diff --git a/NEWS.md b/NEWS.md
index c8cd96392f..8e4cd5b176 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -129,6 +129,7 @@
 
 31. Fixed a bug on Windows where `data.table`s containing non-UTF8 strings in `key`s were not properly sorted, [#2462](https://github.com/Rdatatable/data.table/issues/2462), [#1826](https://github.com/Rdatatable/data.table/issues/1826)  and [StackOverflow](https://stackoverflow.com/questions/47599934/why-doesnt-r-data-table-support-well-for-non-ascii-keys-on-windows). Thanks to @shrektan for reporting and fixing.
 
+32. `x.` prefixes during joins sometimes resulted in a "column not found" error. This is now fixed. Closes [#2313](https://github.com/Rdatatable/data.table/issues/2313). Thanks to @franknarf1 for the MRE.
 
 #### NOTES
 
diff --git a/R/data.table.R b/R/data.table.R
index 895649c724..6b1b33b9be 100644
--- a/R/data.table.R
+++ b/R/data.table.R
@@ -1504,7 +1504,7 @@ chmatch2 <- function(x, table, nomatch=NA_integer_) {
   if (length(xcols)) {
     #  TODO add: if (length(alloc)==nrow(x)) stop("There is no need to deep copy x in this case")
     SDenv$.SDall = .Call(CsubsetDT,x,alloc,xcols)    # must be deep copy when largest group is a subset
-    if (xdotcols) setattr(SDenv$.SDall, 'names', ansvars[seq_along(xcols)]) # now that we allow 'x.' prefix in 'j'
+    if (xdotcols) setattr(SDenv$.SDall, 'names', ansvars[xcolsAns]) # now that we allow 'x.' prefix in 'j', #2313 bug fix - [xcolsAns]
     SDenv$.SD = if (!length(othervars)) SDenv$.SDall else shallow(SDenv$.SDall, setdiff(ansvars, othervars))
   }
   if (nrow(SDenv$.SDall)==0L) {
diff --git a/inst/tests/tests.Rraw b/inst/tests/tests.Rraw
index 3da75efae9..a8d9e08159 100644
--- a/inst/tests/tests.Rraw
+++ b/inst/tests/tests.Rraw
@@ -11337,6 +11337,18 @@ test(1867.14, fread(f), data.table(V1=1:9, x=DT$x, y=DT$y, v=DT$v), warning="Add
 unlink(f)
 # test(1867.15, fread(testDir("iterations.txt"))) # #1416 TODO (trailing tabs on most but not at the beginning and a "-" intended to mean missing but taken as text column name)
 
+# non equi joins bug fix #2313
+dt <- data.table(
+  patient.id = c(1L, 2L, 1L, 1L, 2L, 2L, 2L),
+  h.date = as.Date(c("2013/10/15", "2014/10/15", "2015/7/16", "2016/1/7", 
+                                   "2015/12/20", "2015/12/25", "2016/2/10")))
+setorder(dt)
+dt[, `:=`(start.date = h.date - 365, end.date = h.date)]
+# This line below would error without this fix
+ans <- dt[dt, on = .(patient.id, h.date >= start.date, h.date <= end.date),
+         .(patient.id, i.start.date, i.end.date, g = .GRP, .N, x.h.date),
+         by=.EACHI]
+test(1868, "x.h.date" %in% names(ans), TRUE)
 
 ##########################