diff --git a/Makefile b/Makefile
index a5757d1..82b1f6f 100644
--- a/Makefile
+++ b/Makefile
@@ -1,9 +1,9 @@
 PACKAGE	= PDFViewer
 VERSION	= 0.0.0
 SUBDIRS	= data src
-RM	= rm -f
-LN	= ln -f
-TAR	= tar -czvf
+RM	?= rm -f
+LN	?= ln -f
+TAR	?= tar -czvf
 
 
 all: subdirs
diff --git a/data/Makefile b/data/Makefile
index 1cdc51c..6d159ff 100644
--- a/data/Makefile
+++ b/data/Makefile
@@ -1,8 +1,8 @@
 PREFIX	= /usr/local
 DESTDIR	=
-MKDIR	= mkdir -p
-INSTALL	= install
-RM	= rm -f
+MKDIR	?= mkdir -p
+INSTALL	?= install
+RM	?= rm -f
 
 
 all:
diff --git a/src/Makefile b/src/Makefile
index befca44..858ebcf 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -4,15 +4,15 @@ DESTDIR	=
 BINDIR	= $(PREFIX)/bin
 CC	= cc
 CPPFLAGSF= -I $(PREFIX)/include
-CPPFLAGS=
+CPPFLAGS?=
 CFLAGSF	= -W `pkg-config --cflags libDesktop poppler-glib`
 CFLAGS	= -Wall -g -O2 -pedantic
 LDFLAGSF= `pkg-config --libs libDesktop poppler-glib` -lm
 LDFLAGS	= 
-RM	= rm -f
-LN	= ln -f
-MKDIR	= mkdir -p
-INSTALL	= install
+RM	?= rm -f
+LN	?= ln -f
+MKDIR	?= mkdir -p
+INSTALL	?= install
 
 
 all: $(TARGETS)