diff --git a/easybuild/easyconfigs/r/R/R-3.5.0-iomkl-2018a-X11-20180131.eb b/easybuild/easyconfigs/r/R/R-3.5.0-iomkl-2018a-X11-20180131.eb
index b5ababcb2d4b..7c15c4437a82 100644
--- a/easybuild/easyconfigs/r/R/R-3.5.0-iomkl-2018a-X11-20180131.eb
+++ b/easybuild/easyconfigs/r/R/R-3.5.0-iomkl-2018a-X11-20180131.eb
@@ -70,15 +70,21 @@ exts_default_options = {
 # !! order of packages is important !!
 # packages updated on June 20 2018
 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', '0.6-7', {
diff --git a/easybuild/easyconfigs/r/R/R-3.5.1-foss-2018b-Python-2.7.15.eb b/easybuild/easyconfigs/r/R/R-3.5.1-foss-2018b-Python-2.7.15.eb
index ade3dc827cc0..b13278061d05 100644
--- a/easybuild/easyconfigs/r/R/R-3.5.1-foss-2018b-Python-2.7.15.eb
+++ b/easybuild/easyconfigs/r/R/R-3.5.1-foss-2018b-Python-2.7.15.eb
@@ -71,15 +71,21 @@ exts_default_options = {
 # !! order of packages is important !!
 # packages updated on Aug 17, 2018
 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', '0.6-7', {
diff --git a/easybuild/easyconfigs/r/R/R-3.5.1-foss-2018b.eb b/easybuild/easyconfigs/r/R/R-3.5.1-foss-2018b.eb
index 42f68a958e81..72905166d7df 100644
--- a/easybuild/easyconfigs/r/R/R-3.5.1-foss-2018b.eb
+++ b/easybuild/easyconfigs/r/R/R-3.5.1-foss-2018b.eb
@@ -69,15 +69,21 @@ exts_default_options = {
 # !! order of packages is important !!
 # packages updated on Aug 17, 2018
 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', '0.6-7', {
diff --git a/easybuild/easyconfigs/r/R/R-3.5.1-intel-2018b.eb b/easybuild/easyconfigs/r/R/R-3.5.1-intel-2018b.eb
index 191e19260536..4fad425acdd1 100644
--- a/easybuild/easyconfigs/r/R/R-3.5.1-intel-2018b.eb
+++ b/easybuild/easyconfigs/r/R/R-3.5.1-intel-2018b.eb
@@ -69,15 +69,21 @@ exts_default_options = {
 # !! order of packages is important !!
 # packages updated on Aug 17, 2018
 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', '0.6-7', {
diff --git a/easybuild/easyconfigs/r/R/R-3.6.0-foss-2019a.eb b/easybuild/easyconfigs/r/R/R-3.6.0-foss-2019a.eb
index 305cfe5d42eb..b3dfeeb10127 100644
--- a/easybuild/easyconfigs/r/R/R-3.6.0-foss-2019a.eb
+++ b/easybuild/easyconfigs/r/R/R-3.6.0-foss-2019a.eb
@@ -71,15 +71,21 @@ exts_default_options = {
 # !! order of packages is important !!
 # packages updated on June 7, 2019
 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-3.6.0-intel-2019a.eb b/easybuild/easyconfigs/r/R/R-3.6.0-intel-2019a.eb
index a60bcfdbb348..190263d2d3cf 100644
--- a/easybuild/easyconfigs/r/R/R-3.6.0-intel-2019a.eb
+++ b/easybuild/easyconfigs/r/R/R-3.6.0-intel-2019a.eb
@@ -71,15 +71,21 @@ exts_default_options = {
 # !! order of packages is important !!
 # packages updated on June 7, 2019
 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-3.6.2-foss-2019b.eb b/easybuild/easyconfigs/r/R/R-3.6.2-foss-2019b.eb
index fea6a7d12301..0bc641a52fc2 100644
--- a/easybuild/easyconfigs/r/R/R-3.6.2-foss-2019b.eb
+++ b/easybuild/easyconfigs/r/R/R-3.6.2-foss-2019b.eb
@@ -77,15 +77,21 @@ exts_default_options = {
 # !! order of packages is important !!
 # packages updated on 16 December 2019
 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-3.6.2-intel-2019b.eb b/easybuild/easyconfigs/r/R/R-3.6.2-intel-2019b.eb
index 368d1c5b59ad..cabb0423e804 100644
--- a/easybuild/easyconfigs/r/R/R-3.6.2-intel-2019b.eb
+++ b/easybuild/easyconfigs/r/R/R-3.6.2-intel-2019b.eb
@@ -75,15 +75,21 @@ exts_default_options = {
 # !! order of packages is important !!
 # packages updated on 16 December 2019
 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-3.6.3-foss-2020a.eb b/easybuild/easyconfigs/r/R/R-3.6.3-foss-2020a.eb
index 152ea2ef9217..dc8f3642b9a5 100644
--- a/easybuild/easyconfigs/r/R/R-3.6.3-foss-2020a.eb
+++ b/easybuild/easyconfigs/r/R/R-3.6.3-foss-2020a.eb
@@ -71,15 +71,21 @@ exts_default_options = {
 # !! order of packages is important !!
 # packages updated on 25 March 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', {