diff --git a/tf-psa-crypto/CMakeLists.txt b/tf-psa-crypto/CMakeLists.txt
index 3669da3..6e9789a 100644
--- a/tf-psa-crypto/CMakeLists.txt
+++ b/tf-psa-crypto/CMakeLists.txt
@@ -35,6 +35,9 @@
     set(CMAKE_INSTALL_LIBDIR "${LIB_INSTALL_DIR}")
 endif()
 
+# Set the project root directory.
+set(TF_PSA_CRYPTO_DIR ${CMAKE_CURRENT_SOURCE_DIR})
+
 add_subdirectory(include)
 add_subdirectory(core)
 add_subdirectory(drivers)
diff --git a/tf-psa-crypto/core/CMakeLists.txt b/tf-psa-crypto/core/CMakeLists.txt
index c138ab3..dfc292c 100644
--- a/tf-psa-crypto/core/CMakeLists.txt
+++ b/tf-psa-crypto/core/CMakeLists.txt
@@ -129,11 +129,11 @@
     # from core/ and drivers/builtin/src/.
     target_include_directories(${target}
         PUBLIC $<BUILD_INTERFACE:${MBEDTLS_DIR}/include/>
-               $<BUILD_INTERFACE:${MBEDTLS_DIR}/tf-psa-crypto/include/>
-               $<BUILD_INTERFACE:${MBEDTLS_DIR}/tf-psa-crypto/drivers/builtin/include/>
+               $<BUILD_INTERFACE:${TF_PSA_CRYPTO_DIR}/include/>
+               $<BUILD_INTERFACE:${TF_PSA_CRYPTO_DIR}/drivers/builtin/include/>
                $<INSTALL_INTERFACE:include/>
-        PRIVATE ${MBEDTLS_DIR}/tf-psa-crypto/core
-                ${MBEDTLS_DIR}/tf-psa-crypto/drivers/builtin/src
+        PRIVATE ${TF_PSA_CRYPTO_DIR}/core
+                ${TF_PSA_CRYPTO_DIR}/drivers/builtin/src
                 # Needed to include psa_crypto_driver_wrappers.h
                 ${CMAKE_CURRENT_BINARY_DIR})
     # Pass-through MBEDTLS_CONFIG_FILE and MBEDTLS_USER_CONFIG_FILE
diff --git a/tf-psa-crypto/drivers/builtin/CMakeLists.txt b/tf-psa-crypto/drivers/builtin/CMakeLists.txt
index ab9895f..ed2c0f8 100644
--- a/tf-psa-crypto/drivers/builtin/CMakeLists.txt
+++ b/tf-psa-crypto/drivers/builtin/CMakeLists.txt
@@ -128,8 +128,8 @@
       PUBLIC $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/src>
              $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
              $<BUILD_INTERFACE:${MBEDTLS_DIR}/include>
-             $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/../../include>
-      PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/../../core)
+             $<BUILD_INTERFACE:${TF_PSA_CRYPTO_DIR}/include>
+      PRIVATE ${TF_PSA_CRYPTO_DIR}/core)
 
     # Pass-through MBEDTLS_CONFIG_FILE and MBEDTLS_USER_CONFIG_FILE
     # This must be duplicated from library/CMakeLists.txt because
diff --git a/tf-psa-crypto/drivers/everest/CMakeLists.txt b/tf-psa-crypto/drivers/everest/CMakeLists.txt
index 4958a79..82a8597 100644
--- a/tf-psa-crypto/drivers/everest/CMakeLists.txt
+++ b/tf-psa-crypto/drivers/everest/CMakeLists.txt
@@ -8,13 +8,13 @@
 target_include_directories(${everest_target}
   PUBLIC $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
          $<BUILD_INTERFACE:${MBEDTLS_DIR}/include>
-         $<BUILD_INTERFACE:${MBEDTLS_DIR}/tf-psa-crypto/include>
-         $<BUILD_INTERFACE:${MBEDTLS_DIR}/tf-psa-crypto/drivers/builtin/include>
+         $<BUILD_INTERFACE:${TF_PSA_CRYPTO_DIR}/include>
+         $<BUILD_INTERFACE:${TF_PSA_CRYPTO_DIR}/drivers/builtin/include>
          $<INSTALL_INTERFACE:include>
   PRIVATE include/everest
           include/everest/kremlib
           ${MBEDTLS_DIR}/library
-          ${MBEDTLS_DIR}/tf-psa-crypto/core)
+          ${TF_PSA_CRYPTO_DIR}/core)
 
 # Pass-through MBEDTLS_CONFIG_FILE and MBEDTLS_USER_CONFIG_FILE
 # This must be duplicated from library/CMakeLists.txt because
diff --git a/tf-psa-crypto/drivers/p256-m/CMakeLists.txt b/tf-psa-crypto/drivers/p256-m/CMakeLists.txt
index f097ed1..165ee15 100644
--- a/tf-psa-crypto/drivers/p256-m/CMakeLists.txt
+++ b/tf-psa-crypto/drivers/p256-m/CMakeLists.txt
@@ -8,11 +8,11 @@
   PUBLIC $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}>
          $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/p256-m>
          $<BUILD_INTERFACE:${MBEDTLS_DIR}/include>
-         $<BUILD_INTERFACE:${MBEDTLS_DIR}/tf-psa-crypto/include>
-         $<BUILD_INTERFACE:${MBEDTLS_DIR}/tf-psa-crypto/drivers/builtin/include>
+         $<BUILD_INTERFACE:${TF_PSA_CRYPTO_DIR}/include>
+         $<BUILD_INTERFACE:${TF_PSA_CRYPTO_DIR}/drivers/builtin/include>
          $<INSTALL_INTERFACE:include>
   PRIVATE ${MBEDTLS_DIR}/library/
-          ${MBEDTLS_DIR}/tf-psa-crypto/core)
+          ${TF_PSA_CRYPTO_DIR}/core)
 
 # Pass-through MBEDTLS_CONFIG_FILE and MBEDTLS_USER_CONFIG_FILE
 # This must be duplicated from library/CMakeLists.txt because