diff --git a/inst/tests/tests.Rraw b/inst/tests/tests.Rraw
index 182fc41dc..8c9f3f425 100644
--- a/inst/tests/tests.Rraw
+++ b/inst/tests/tests.Rraw
@@ -5878,7 +5878,8 @@ DT <- data.table(intCol    = sample(c(1:3, NA), n, replace = TRUE),
                  doubleCol = sample(c(1.86, 1000.345, 2.346, NA, NaN), n, replace = TRUE),
                  boolCol   = sample(c(TRUE, FALSE, NA), n, replace = TRUE),
                  charCol   = sample(c(LETTERS[1:3], NA), n, replace = TRUE),
-                 groupCol  = sample(c("a", "b", "c"), n, replace = TRUE))
+                 groupCol  = sort(sample(c("a", "b", "c"), n, replace = TRUE)) ## sort is important to test #2713
+                 )
 if (test_bit64) DT[, int64Col := as.integer64(sample(1:3, n, replace = TRUE))]
 ## get list with unique values excluding NA
 vals <- lapply(DT, function(x) {out <- unique(x); out[!is.na(out)]})