diff --git a/Makefile.config.in b/Makefile.config.in
index 25e537bcc..e5a6f4c68 100644
--- a/Makefile.config.in
+++ b/Makefile.config.in
@@ -1,3 +1,7 @@
+CC = @CC@
+CFLAGS = @CFLAGS@
+CXX = @CXX@
+CXXFLAGS = @CXXFLAGS@
 PACKAGE_NAME = @PACKAGE_NAME@
 PACKAGE_VERSION = @PACKAGE_VERSION@
 bindir = @bindir@
diff --git a/Makefile.lib b/Makefile.lib
index c7880ff11..449f19ad5 100644
--- a/Makefile.lib
+++ b/Makefile.lib
@@ -5,10 +5,10 @@ here = $(dir $(lastword $(MAKEFILE_LIST)))
 QUIET = @
 
 %.o: %.cc
-	$(QUIET) g++ -o $@ -c $< -g -fPIC $(CXXFLAGS) $($@_CXXFLAGS) -MMD -MF $(basename $@).dep -MP
+	$(QUIET) $(CXX) -o $@ -c $< -g -fPIC $(CXXFLAGS) $($@_CXXFLAGS) -MMD -MF $(basename $@).dep -MP
 
 %.o: %.c
-	$(QUIET) gcc -o $@ -c $< -g -fPIC $(CFLAGS) $($@_CFLAGS) -MMD -MF $(basename $@).dep -MP
+	$(QUIET) $(CC) -o $@ -c $< -g -fPIC $(CFLAGS) $($@_CFLAGS) -MMD -MF $(basename $@).dep -MP
 
 
 # Generate Make rules for libraries.
diff --git a/Makefile.new b/Makefile.new
index 566f1f7be..8911d6d72 100644
--- a/Makefile.new
+++ b/Makefile.new
@@ -12,9 +12,7 @@ include src/nix-instantiate/Makefile.new
 include src/nix-env/Makefile.new
 include src/nix-daemon/Makefile.new
 
-CXXFLAGS = -I . -I src -I src/libutil -I src/libstore -I src/libmain -I src/libexpr
-
-CFLAGS =
+CXXFLAGS += -I . -I src -I src/libutil -I src/libstore -I src/libmain -I src/libexpr
 
 $(foreach lib, $(LIBS), $(eval $(call LIBS_template,$(lib))))
 $(foreach prog, $(PROGRAMS), $(eval $(call PROGRAMS_template,$(prog))))