diff --git a/guix/build-system/r.scm b/guix/build-system/r.scm
index 565c7db344..f14a4c61c0 100644
--- a/guix/build-system/r.scm
+++ b/guix/build-system/r.scm
@@ -110,7 +110,7 @@ release corresponding to NAME and VERSION."
                   (tests? #t)
                   (test-target "tests")
                   (test-types #f)
-                  test-directory
+                  (test-directory "tests/testthat")
                   skipped-tests
                   (configure-flags ''())
                   (phases '%standard-phases)
diff --git a/guix/build/r-build-system.scm b/guix/build/r-build-system.scm
index b32df93d2d..2473d61a6f 100644
--- a/guix/build/r-build-system.scm
+++ b/guix/build/r-build-system.scm
@@ -72,7 +72,7 @@
 each consisting of a file name under TEST-DIRECTORY and one or more names of
 tests to be skipped.  If the entry is just a file name, delete the test file."
   (when skipped-tests
-    (with-directory-excursion "tests/testthat/"
+    (with-directory-excursion test-directory
       (for-each (match-lambda
                   ((file test-names ...)
                    (substitute file