diff --git a/library/CMakeLists.txt b/library/CMakeLists.txt
index 5cb5ec860f..5b75b6460c 100644
--- a/library/CMakeLists.txt
+++ b/library/CMakeLists.txt
@@ -1,10 +1,3 @@
-# Set the project root directory if it's not already defined, as may happen if
-# the library folder is included directly by a parent project, without
-# including the top level CMakeLists.txt.
-if(NOT DEFINED MBEDTLS_DIR)
-    set(MBEDTLS_DIR ${CMAKE_SOURCE_DIR})
-endif()
-
 set(src_x509
     pkcs7.c
     x509.c
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 4e90bffb3a..a9d5c842b8 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -3,13 +3,6 @@ set(libs
     ${CMAKE_THREAD_LIBS_INIT}
 )
 
-# Set the project root directory if it's not already defined, as may happen if
-# the tests folder is included directly by a parent project, without including
-# the top level CMakeLists.txt.
-if(NOT DEFINED MBEDTLS_DIR)
-    set(MBEDTLS_DIR ${CMAKE_SOURCE_DIR})
-endif()
-
 if(NOT MBEDTLS_PYTHON_EXECUTABLE)
     message(FATAL_ERROR "Cannot build test suites without Python 3")
 endif()
diff --git a/tf-psa-crypto/tests/CMakeLists.txt b/tf-psa-crypto/tests/CMakeLists.txt
index 862d8623b0..4755cae73d 100644
--- a/tf-psa-crypto/tests/CMakeLists.txt
+++ b/tf-psa-crypto/tests/CMakeLists.txt
@@ -3,13 +3,6 @@ set(libs
     ${CMAKE_THREAD_LIBS_INIT}
 )
 
-# Set the project root directory if it's not already defined, as may happen if
-# the tests folder is included directly by a parent project, without including
-# the top level CMakeLists.txt.
-if(NOT DEFINED MBEDTLS_DIR)
-    set(MBEDTLS_DIR ${CMAKE_SOURCE_DIR})
-endif()
-
 if(NOT TF_PSA_CRYPTO_PYTHON_EXECUTABLE)
     message(FATAL_ERROR "Cannot build test suites without Python 3")
 endif()