diff --git a/repo2docker/buildpacks/r.py b/repo2docker/buildpacks/r.py
index 41a1765c..4dcbbb10 100644
--- a/repo2docker/buildpacks/r.py
+++ b/repo2docker/buildpacks/r.py
@@ -63,8 +63,9 @@ class RBuildPack(PythonBuildPack):
         Will return the version specified by the user or the current default
         version.
         """
+        # Available versions at https://cran.r-project.org/src/base/
         version_map = {
-            "4.2": "4.2.0",
+            "4.2": "4.2.1",
             "4.1": "4.1.3",
             "4.0": "4.0.5",
             "3.6": "3.6.3",
@@ -75,6 +76,11 @@ class RBuildPack(PythonBuildPack):
 
         # the default if nothing is specified
         # Use full version is needed here, so it a valid semver
+        #
+        # NOTE: When updating this version, also update
+        #       - tests/unit/test_r.py -> test_version_specification
+        #       - tests/r/simple/verify
+        #
         r_version = version_map["4.2"]
 
         if not hasattr(self, "_r_version"):
diff --git a/tests/unit/test_r.py b/tests/unit/test_r.py
index 6298914b..f13ee739 100644
--- a/tests/unit/test_r.py
+++ b/tests/unit/test_r.py
@@ -8,7 +8,7 @@ from repo2docker import buildpacks
 
 
 @pytest.mark.parametrize(
-    "runtime_version, expected", [("", "4.1"), ("3.6", "3.6"), ("3.5.1", "3.5")]
+    "runtime_version, expected", [("", "4.2"), ("3.6", "3.6"), ("3.5.1", "3.5")]
 )
 def test_version_specification(tmpdir, runtime_version, expected):
     tmpdir.chdir()