diff --git a/Makefile b/Makefile
index 2a00a76940..349c50b67d 100644
--- a/Makefile
+++ b/Makefile
@@ -129,7 +129,8 @@ TEXTURE_FILES_OUT := $(foreach f,$(TEXTURE_FILES_PNG:.png=.inc.c),build/$f) \
 					 $(foreach f,$(TEXTURE_FILES_JPG:.jpg=.jpg.inc.c),build/$f) \
 
 C_FILES       := $(foreach dir,$(SRC_DIRS),$(wildcard $(dir)/*.c))
-S_FILES       := $(foreach dir,$(ASM_DIRS),$(wildcard $(dir)/*.s))
+S_FILES       := $(shell grep -F "build/asm" spec | sed 's/.*build\/// ; s/\.o\".*/.s/') \
+                 $(shell grep -F "build/data" spec | sed 's/.*build\/// ; s/\.o\".*/.s/')
 O_FILES       := $(foreach f,$(S_FILES:.s=.o),build/$f) \
                  $(foreach f,$(wildcard baserom/*),build/$f.o) \
                  $(foreach f,$(C_FILES:.c=.o),build/$f) \