diff --git a/src/rp2_common/cmsis/BUILD.bazel b/src/rp2_common/cmsis/BUILD.bazel
index 782b39d5a..f7fca7be7 100644
--- a/src/rp2_common/cmsis/BUILD.bazel
+++ b/src/rp2_common/cmsis/BUILD.bazel
@@ -7,12 +7,16 @@ package(default_visibility = ["//visibility:public"])
 cc_library(
     name = "rename_exceptions",
     hdrs = ["include/cmsis/rename_exceptions.h"],
+    # This is mildly odd, but intentional. We really don't want this header
+    # to have extra deps, but this should always be defined.
+    defines = ["LIB_CMSIS_CORE=1"],
     includes = ["include"],
     target_compatible_with = compatible_with_rp2(),
 )
 
 cc_library(
     name = "cmsis_core",
+    defines = ["LIB_CMSIS_CORE=1"],
     srcs = [
         "stub/CMSIS/Device/RaspberryPi/RP2040/Source/system_RP2040.c",
     ],
diff --git a/src/rp2_common/pico_cyw43_arch/BUILD.bazel b/src/rp2_common/pico_cyw43_arch/BUILD.bazel
index 32854da36..a17fc2a64 100644
--- a/src/rp2_common/pico_cyw43_arch/BUILD.bazel
+++ b/src/rp2_common/pico_cyw43_arch/BUILD.bazel
@@ -34,6 +34,7 @@ _CONFIGURATIONS = [
             "include/pico/cyw43_arch/arch_{}.h".format(kind),
         ],
         defines = [
+            "LIB_PICO_CYW43_ARCH=1",
             "PICO_CYW43_ARCH_{}=1".format(kind.upper()),
             "CYW43_LWIP={}".format(1 if use_lwip else 0),
         ],