diff --git a/CHANGES b/CHANGES
index 584b302..6b3f570 100644
--- a/CHANGES
+++ b/CHANGES
@@ -2,6 +2,7 @@ i2c-tools CHANGES
 -----------------
 
 SVN
+  Makefile: Let the environment set CC and CFLAGS
   decode-dimms: Handle CRC of FB-DIMM and DDR3 SDRAM memory modules
                 Add support for DDR3 SDRAM
                 Fix decoding of SDR SDRAM bytes 12-14
diff --git a/Makefile b/Makefile
index edb4e80..8816020 100644
--- a/Makefile
+++ b/Makefile
@@ -21,12 +21,12 @@ INSTALL_DIR	:= $(INSTALL) -m 755 -d
 INSTALL_PROGRAM	:= $(INSTALL) -m 755
 RM		:= rm -f
 
-CC	:= gcc
-CFLAGS	:= -Wall
+CC	?= gcc
 
-CFLAGS	+= -O2
+CFLAGS	?= -O2
 # When debugging, use the following instead
-#CFLAGS	+= -O -g
+#CFLAGS	:= -O -g
+CFLAGS	+= -Wall
 
 KERNELVERSION	:= $(shell uname -r)