diff --git a/CMakeLists.txt b/CMakeLists.txt
index 02216f5..f180d2e 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -154,6 +154,8 @@ external/mx25519/src/portable/scalarmult.c
 
 if(CMAKE_SYSTEM_PROCESSOR MATCHES "x86_64" OR CMAKE_SYSTEM_PROCESSOR MATCHES "AMD64" OR CMAKE_SYSTEM_PROCESSOR MATCHES "amd64")
 	list(APPEND SOURCES external/mx25519/src/amd64/scalarmult_gnu.S)
+	# Treat asm as C to keep clang/MinGW happy when emitting .obj
+	set_source_files_properties(external/mx25519/src/amd64/scalarmult_gnu.S PROPERTIES LANGUAGE C)
 endif()
 if(CMAKE_SYSTEM_PROCESSOR MATCHES "aarch64" OR CMAKE_SYSTEM_PROCESSOR MATCHES "arm64" OR CMAKE_SYSTEM_PROCESSOR MATCHES "armv8")
 	list(APPEND SOURCES external/mx25519/src/arm64/scalarmult.S)