diff --git a/Makefile b/Makefile
index 6c380664..d98021c4 100644
--- a/Makefile
+++ b/Makefile
@@ -61,13 +61,14 @@ SRC	    = $(wildcard src/*.cpp)
 OBJS        = $(SRC:src/%.cpp=build/%.o)
 DEPS        = $(SRC:src/%.cpp=build/%.d)
 MANPAGE     = mergerfs.1
-CXXFLAGS    = \
+CXXFLAGS    ?= ${OPT_FLAGS}
+CXXFLAGS    := \
+              ${CXXFLAGS} \
               -std=c++0x \
-              $(OPT_FLAGS) \
               $(STATIC_FLAGS) \
               $(LTO_FLAGS) \
               -Wall \
-	      -Wno-unused-result \
+              -Wno-unused-result \
               -MMD
 FUSE_FLAGS = \
               -Ilibfuse/include \
@@ -76,9 +77,11 @@ FUSE_FLAGS = \
 MFS_FLAGS  = \
 	      -DUSE_XATTR=$(USE_XATTR) \
 	      -DUGID_USE_RWLOCK=$(UGID_USE_RWLOCK)
-LDFLAGS    = \
-	      -pthread \
-              -lrt
+
+LDFLAGS := \
+    ${LDFLAGS} \
+    -pthread \
+    -lrt
 
 DESTDIR       =
 PREFIX        = /usr/local
diff --git a/libfuse/Makefile b/libfuse/Makefile
index e3001aa3..2bbc45a0 100644
--- a/libfuse/Makefile
+++ b/libfuse/Makefile
@@ -29,6 +29,8 @@ INSTALLBINDIR  = $(DESTDIR)$(BINDIR)
 INSTALLSBINDIR = $(DESTDIR)$(SBINDIR)
 INSTALLMAN1DIR = $(DESTDIR)$(MAN1DIR)
 
+AR ?= ar
+
 SRC   = \
 	lib/buffer.c \
 	lib/cuse_lowlevel.c \
@@ -46,9 +48,10 @@ SRC   = \
 	lib/mount.c
 OBJS = $(SRC:lib/%.c=build/%.o)
 DEPS = $(SRC:lib/%.c=build/%.d)
-
-CFLAGS = \
-	$(OPT_FLAGS) \
+CFLAGS ?= \
+	$(OPT_FLAGS)
+CFLAGS := \
+    ${CFLAGS} \
 	-Wall \
 	-pipe \
 	-MMD
@@ -61,7 +64,8 @@ FUSE_FLAGS = \
 	-DFUSE_USE_VERSION=29 \
 	-DPACKAGE_VERSION=\"$(VERSION)\" \
 	-DFUSERMOUNT_DIR=\"$(FUSERMOUNT_DIR)\"
-LDFLAGS = \
+LDFLAGS := \
+	${LDFLAGS} \
 	-lrt \
 	-pthread
 
@@ -78,7 +82,7 @@ objects: build/config.h
 	$(MAKE) $(OBJS)
 
 build/libfuse.a: objects
-	ar rcs build/libfuse.a $(OBJS)
+	${AR} rcs build/libfuse.a $(OBJS)
 
 utils: mergerfs-fusermount mount.mergerfs