diff --git a/easybuild/easyconfigs/r/R/R-4.0.0-foss-2020a.eb b/easybuild/easyconfigs/r/R/R-4.0.0-foss-2020a.eb
index e4788de50ef..9afb0e13b61 100644
--- a/easybuild/easyconfigs/r/R/R-4.0.0-foss-2020a.eb
+++ b/easybuild/easyconfigs/r/R/R-4.0.0-foss-2020a.eb
@@ -77,15 +77,21 @@ exts_default_options = {
 # !! order of packages is important !!
 # packages updated on 23 July 2020
 exts_list = [
+    # include packages that are part of the base installation of R,
+    # both to make sure they are available (via sanity check),
+    # and to be able to pass the check for required dependencies when installing extensions in parallel
     'base',
+    'compiler',
     'datasets',
     'graphics',
     'grDevices',
     'grid',
     'methods',
+    'parallel',
     'splines',
     'stats',
     'stats4',
+    'tcltk',
     'tools',
     'utils',
     ('Rmpi', '0.6-9', {
diff --git a/easybuild/easyconfigs/r/R/R-4.0.3-foss-2020b.eb b/easybuild/easyconfigs/r/R/R-4.0.3-foss-2020b.eb
index d8bbd8572a8..3226ee0f4bc 100644
--- a/easybuild/easyconfigs/r/R/R-4.0.3-foss-2020b.eb
+++ b/easybuild/easyconfigs/r/R/R-4.0.3-foss-2020b.eb
@@ -74,15 +74,21 @@ exts_default_options = {
 # !! order of packages is important !!
 # packages updated on 10 Nov 2020
 exts_list = [
+    # include packages that are part of the base installation of R,
+    # both to make sure they are available (via sanity check),
+    # and to be able to pass the check for required dependencies when installing extensions in parallel
     'base',
+    'compiler',
     'datasets',
     'graphics',
     'grDevices',
     'grid',
     'methods',
+    'parallel',
     'splines',
     'stats',
     'stats4',
+    'tcltk',
     'tools',
     'utils',
     ('Rmpi', '0.6-9', {
diff --git a/easybuild/easyconfigs/r/R/R-4.0.4-foss-2020b.eb b/easybuild/easyconfigs/r/R/R-4.0.4-foss-2020b.eb
index e3dbbcb551d..26d6cbdb27b 100644
--- a/easybuild/easyconfigs/r/R/R-4.0.4-foss-2020b.eb
+++ b/easybuild/easyconfigs/r/R/R-4.0.4-foss-2020b.eb
@@ -81,15 +81,21 @@ exts_default_options = {
 # !! order of packages is important !!
 # packages updated on 08 Mar 2021
 exts_list = [
+    # include packages that are part of the base installation of R,
+    # both to make sure they are available (via sanity check),
+    # and to be able to pass the check for required dependencies when installing extensions in parallel
     'base',
+    'compiler',
     'datasets',
     'graphics',
     'grDevices',
     'grid',
     'methods',
+    'parallel',
     'splines',
     'stats',
     'stats4',
+    'tcltk',
     'tools',
     'utils',
     ('Rmpi', '0.6-9.1', {
diff --git a/easybuild/easyconfigs/r/R/R-4.0.5-foss-2020b.eb b/easybuild/easyconfigs/r/R/R-4.0.5-foss-2020b.eb
index d1f3feab30c..febdb0ca5e7 100644
--- a/easybuild/easyconfigs/r/R/R-4.0.5-foss-2020b.eb
+++ b/easybuild/easyconfigs/r/R/R-4.0.5-foss-2020b.eb
@@ -78,15 +78,21 @@ exts_default_options = {
 # !! order of packages is important !!
 # packages updated on 07 Apr 2021
 exts_list = [
+    # include packages that are part of the base installation of R,
+    # both to make sure they are available (via sanity check),
+    # and to be able to pass the check for required dependencies when installing extensions in parallel
     'base',
+    'compiler',
     'datasets',
     'graphics',
     'grDevices',
     'grid',
     'methods',
+    'parallel',
     'splines',
     'stats',
     'stats4',
+    'tcltk',
     'tools',
     'utils',
     ('Rmpi', '0.6-9.1', {
diff --git a/easybuild/easyconfigs/r/R/R-4.1.0-foss-2021a.eb b/easybuild/easyconfigs/r/R/R-4.1.0-foss-2021a.eb
index 6a6012353a2..d50895fcfd0 100644
--- a/easybuild/easyconfigs/r/R/R-4.1.0-foss-2021a.eb
+++ b/easybuild/easyconfigs/r/R/R-4.1.0-foss-2021a.eb
@@ -79,15 +79,21 @@ exts_default_options = {
 # !! order of packages is important !!
 # packages updated on 3rd June 2021
 exts_list = [
+    # include packages that are part of the base installation of R,
+    # both to make sure they are available (via sanity check),
+    # and to be able to pass the check for required dependencies when installing extensions in parallel
     'base',
+    'compiler',
     'datasets',
     'graphics',
     'grDevices',
     'grid',
     'methods',
+    'parallel',
     'splines',
     'stats',
     'stats4',
+    'tcltk',
     'tools',
     'utils',
     ('Rmpi', '0.6-9.1', {