diff --git a/NEWS.md b/NEWS.md
index 94ffe21cd..a7a5c38d6 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -11,6 +11,8 @@ If you read this from a place other than <https://mc-stan.org/projpred/news/inde
 
 ## Bug fixes and maintenance
 
+* Tests: Adapt to version 2.1-0 of package lme4. (GitHub: #577)
+
 
 # projpred 2.11.0
 
diff --git a/tests/testthat/helpers/testers.R b/tests/testthat/helpers/testers.R
index 5c82c55be..c804d74dd 100644
--- a/tests/testthat/helpers/testers.R
+++ b/tests/testthat/helpers/testers.R
@@ -2189,13 +2189,20 @@ vsel_tester <- function(
   # predictor_ranking
   expect_type(vs$predictor_ranking, "character")
   expect_length(vs$predictor_ranking, prd_trms_len_expected)
+  # The search terms include the linear term of each smooth term (e.g., `s.1`
+  # for `s(s.1)`):
+  trms_universe_split_lin <- c(
+    trms_universe_split,
+    sub("^s\\((.*)\\)$", "\\1",
+        grep("^s\\(.*\\)$", trms_universe_split, value = TRUE))
+  )
   rk_fulldata <- vs$predictor_ranking
   for (rk_fulldata_plus in grep("\\+", rk_fulldata, value = TRUE)) {
     rk_fulldata <- setdiff(rk_fulldata, rk_fulldata_plus)
     rk_fulldata <- c(rk_fulldata,
                      labels(terms(as.formula(paste(". ~", rk_fulldata_plus)))))
   }
-  expect_true(all(rk_fulldata %in% trms_universe_split), info = info_str)
+  expect_true(all(rk_fulldata %in% trms_universe_split_lin), info = info_str)
 
   # predictor_ranking_cv
   if (with_cv && isTRUE(vs$validate_search)) {
@@ -2215,14 +2222,8 @@ vsel_tester <- function(
       rk_cv <- setdiff(rk_cv, rk_cv_plus)
       rk_cv <- c(rk_cv, labels(terms(as.formula(paste(". ~", rk_cv_plus)))))
     }
-    expect_true(
-      all(rk_cv %in%
-            c(trms_universe_split,
-              sub("^s\\((.*)\\)$", "\\1",
-                  grep("^s\\(.*\\)$", trms_universe_split, value = TRUE)),
-              NA_character_)),
-      info = info_str
-    )
+    expect_true(all(rk_cv %in% c(trms_universe_split_lin, NA_character_)),
+                info = info_str)
   } else {
     expect_null(vs$predictor_ranking_cv, info = info_str)
   }
diff --git a/tests/testthat/test_augdat.R b/tests/testthat/test_augdat.R
index 35dcbc8ba..1cc3ce707 100644
--- a/tests/testthat/test_augdat.R
+++ b/tests/testthat/test_augdat.R
@@ -219,6 +219,18 @@ test_that(paste(
 
 ## Projection -------------------------------------------------------------
 
+# Whether the submodel of a projection setup has group-level terms. The
+# comparisons of traditional and augmented-data projection below skip such
+# submodels: lme4::glmer() computes the objective for the group-level parameters
+# with binomial()$aic, which rounds non-integer responses (traditional
+# projection) and non-integer weights (augmented-data projection), so the two
+# projections fit different objectives. glmer() rounds with `nAGQ = 1` in all
+# lme4 versions, and since lme4 2.1-0 also with `nAGQ > 1` (the `nAGQ = 30` of
+# these projections in setup.R).
+has_group_terms_prj <- function(args_prj_i) {
+  any(grepl("\\|", args_prj_i$predictor_terms))
+}
+
 test_that(paste(
   "augmented-data and traditional projection give similar results (in case of",
   "the `brnll` family and the default `regul` for submodels fitted by",
@@ -229,6 +241,7 @@ test_that(paste(
   for (tstsetup in tstsetups) {
     tstsetup_trad <- sub("\\.augdat\\.", ".trad_compare.", tstsetup)
     if (!tstsetup_trad %in% names(prjs)) next
+    if (has_group_terms_prj(args_prj[[tstsetup]])) next
 
     cl_used_gt1 <- ndr_ncl_dtls(args_prj[[tstsetup]])$clust_used_gt1
     prjmat <- as.matrix(prjs[[tstsetup]],
@@ -236,12 +249,7 @@ test_that(paste(
     prjmat_trad <- as.matrix(prjs[[tstsetup_trad]],
                              allow_nonconst_wdraws_prj = cl_used_gt1)
 
-    tol_coefs <- ifelse(
-      args_prj[[tstsetup]]$mod_nm == "glmm" &&
-        any(grepl("^\\(.*\\)$", args_prj[[tstsetup]]$predictor_terms)),
-      1e-3, 1e-5
-    )
-    expect_equal(prjmat, prjmat_trad, tolerance = tol_coefs, info = tstsetup)
+    expect_equal(prjmat, prjmat_trad, tolerance = 1e-5, info = tstsetup)
   }
 })
 
@@ -288,6 +296,7 @@ test_that(paste(
   for (tstsetup in tstsetups) {
     tstsetup_trad <- sub("\\.augdat\\.", ".trad_compare.", tstsetup)
     if (!tstsetup_trad %in% names(pls)) next
+    if (has_group_terms_prj(args_prj[[tstsetup]])) next
 
     pl <- pls[[tstsetup]]
     expect_length(dim(pl$pred), 3)
@@ -300,12 +309,7 @@ test_that(paste(
     dimnames(pl$lpd) <- list(NULL, as.character(seq_len(ncol(pl$lpd))))
     pl_trad <- pls[[tstsetup_trad]]
 
-    tol_lpreds <- ifelse(
-      args_prj[[tstsetup]]$mod_nm == "glmm" &&
-        any(grepl("^\\(.*\\)$", args_prj[[tstsetup]]$predictor_terms)),
-      1e-4, 1e-5
-    )
-    expect_equal(pl, pl_trad, tolerance = tol_lpreds, info = tstsetup)
+    expect_equal(pl, pl_trad, tolerance = 1e-5, info = tstsetup)
   }
 })