diff --git a/Makefile b/Makefile
index 3fe8c9d..0c297cd 100644
--- a/Makefile
+++ b/Makefile
@@ -22,10 +22,10 @@ SOURCES = \
 	token_rewriter \
 	token
 
-CPP_FILES = $(foreach source,$(SOURCES),$(source).cpp)
-HPP_FILES = $(foreach source,$(SOURCES),$(source).hpp)
+CPP_FILES = $(addsuffix .cpp,$(SOURCES))
+HPP_FILES = $(addsuffix .hpp,$(SOURCES))
 HPP_FILES += token_ids.hpp
-O_FILES = $(foreach source,$(SOURCES),$(source).$(O))
+O_FILES = $(addsuffix .$(O),$(SOURCES))
 STATIC_LIB = libruby_parser_cpp.$(A)
 
 # Codegen
diff --git a/codegen/build.mk b/codegen/build.mk
index 4fb3430..cd8bd4e 100644
--- a/codegen/build.mk
+++ b/codegen/build.mk
@@ -59,9 +59,8 @@ codegen/merge-headers:
 	chmod +x codegen/merge-headers
 CLEAN += codegen/merge-headers
 
-# A literal space.
-space :=
-space +=
+empty :=
+space := $(empty) $(empty)
 
 # Joins elements of the list in arg 2 with the given separator.
 #   1. Element separator.