diff --git a/echo.bzl b/echo.bzl
index 46f017a..0189f5e 100644
--- a/echo.bzl
+++ b/echo.bzl
@@ -23,6 +23,7 @@
         "@pigweed//pw_assert:backend_impl": "@pigweed//pw_assert_basic:impl",
         "@pigweed//pw_log:backend": "@pigweed//pw_log_basic",
         "@pigweed//pw_log:backend_impl": "@pigweed//pw_log_basic:impl",
+        "@pigweed//pw_sys_io:backend": "@pigweed//pw_sys_io_baremetal_stm32f429",
     }
 
 _stm32_transition = transition(
@@ -35,6 +36,7 @@
         "@pigweed//pw_assert:backend_impl",
         "@pigweed//pw_log:backend",
         "@pigweed//pw_log:backend_impl",
+        "@pigweed//pw_sys_io:backend",
     ],
 )
 
diff --git a/targets/BUILD.bazel b/targets/BUILD.bazel
index c7041cf..5a5ce5b 100644
--- a/targets/BUILD.bazel
+++ b/targets/BUILD.bazel
@@ -16,10 +16,9 @@
     name = "stm32",
     constraint_values = [
         "@pigweed//pw_malloc_freelist:backend",
-        # Use the baremetal backend for stm32f429 defined in upstream Pigweed.
-        "@pigweed//pw_sys_io_baremetal_stm32f429:backend",
         "@platforms//cpu:armv7e-m",
         "@platforms//os:none",
+        "@pigweed//pw_sys_io_baremetal_stm32f429:compatible",
         # Target the cortex-m4. Bazel selects the right toolchain based on
         # this.
         "@pw_toolchain//constraints/arm_mcpu:cortex-m4+nofp",