diff --git a/tools/functions.make b/tools/functions.make
index ccb23102fc..d3fad449bb 100644
--- a/tools/functions.make
+++ b/tools/functions.make
@@ -24,8 +24,7 @@ preprocess = $(shell $(CC) $(PPCFLAGS) $(2) -E -P -x c -include config.h $(1) |
 		grep -v "^$(_hash_)" | grep -v "^ *$$" | \
 		sed -e 's:^..*:$(dir $(1))&:')
 
-preprocess2file = $(shell $(CC) $(PPCFLAGS) $(3) -E -P -x c -include config.h $(1) | \
-		grep -v '^$(_hash_)' | grep -v "^$$" > $(2))
+preprocess2file = $(SILENT)$(CC) $(PPCFLAGS) $(3) -E -P -x c -include config.h $(1) -o $(2)
 
 asmdefs2file = $(SILENT)$(CC) $(PPCFLAGS) $(3) -S -x c -o - -include config.h $(1) | \
 	perl -ne 'if(/^_?AD_(\w+):$$/){$$var=$$1}else{/^\W\.(?:word|long)\W(.*)$$/ && $$var && print "\#define $$var $$1\n";$$var=0}' > $(2)