diff --git a/ports/esp32/esp32_common.cmake b/ports/esp32/esp32_common.cmake
index d6a4aedb85c68..a4f8d394f5c5e 100644
--- a/ports/esp32/esp32_common.cmake
+++ b/ports/esp32/esp32_common.cmake
@@ -225,6 +225,7 @@ idf_component_register(
         ${MICROPY_SOURCE_PORT}
         ${MICROPY_SOURCE_BOARD}
         ${MICROPY_SOURCE_TINYUSB}
+        ${MICROPY_SOURCE_USERMOD}
     INCLUDE_DIRS
         ${MICROPY_INC_CORE}
         ${MICROPY_INC_USERMOD}
diff --git a/ports/rp2/CMakeLists.txt b/ports/rp2/CMakeLists.txt
index 2be74151d87bf..396ad36e5c08a 100644
--- a/ports/rp2/CMakeLists.txt
+++ b/ports/rp2/CMakeLists.txt
@@ -510,6 +510,7 @@ target_sources(${MICROPY_TARGET} PRIVATE
     ${MICROPY_SOURCE_DRIVERS}
     ${MICROPY_SOURCE_PORT}
     ${MICROPY_SOURCE_BOARD}
+    ${MICROPY_SOURCE_USERMOD}
 )
 
 target_link_libraries(${MICROPY_TARGET} micropy_lib_mbedtls)
diff --git a/py/usermod.cmake b/py/usermod.cmake
index 4a8b99ff31b46..e57979e1df080 100644
--- a/py/usermod.cmake
+++ b/py/usermod.cmake
@@ -9,10 +9,12 @@ function(usermod_gather_sources SOURCES_VARNAME INCLUDE_DIRECTORIES_VARNAME INCL
             return()
         endif()
 
-        # Gather library sources
+        # Gather library sources, then clear them from the target to prevent
+        # double compilation when the port also links this INTERFACE library.
         get_target_property(lib_sources ${LIB} INTERFACE_SOURCES)
         if (lib_sources)
             list(APPEND ${SOURCES_VARNAME} ${lib_sources})
+            set_target_properties(${LIB} PROPERTIES INTERFACE_SOURCES "")
         endif()
 
         # Gather library includes