diff --git a/common.mak b/common.mak
index 78985d8b367bac1fa7f031277132e6f2571a0070..21b2273da4f9cd8f283b3896df4064fbe90d0826 100644
--- a/common.mak
+++ b/common.mak
@@ -5,6 +5,9 @@
 SRC_DIR = $(SRC_PATH)/lib$(NAME)
 VPATH = $(SRC_DIR)
 
+CFLAGS += -DHAVE_AV_CONFIG_H -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE \
+          -D_ISOC9X_SOURCE -I$(BUILD_ROOT) -I$(SRC_PATH) \
+          -I$(SRC_PATH)/libavutil $(OPTFLAGS)
 SRCS := $(OBJS:.o=.c) $(ASM_OBJS:.o=.S) $(CPPOBJS:.o=.cpp)
 OBJS := $(OBJS) $(ASM_OBJS) $(CPPOBJS)
 STATIC_OBJS := $(OBJS) $(STATIC_OBJS)
diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index da5236ea9957a638c0f60cd78f67462d36f025e1..3193e749d0765a8b77c2ee278deacbbea4386a8c 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -4,8 +4,7 @@
 #
 include ../config.mak
 
-CFLAGS=-DHAVE_AV_CONFIG_H -I$(BUILD_ROOT) -I$(SRC_PATH)/libavutil $(OPTFLAGS) \
-       -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_ISOC9X_SOURCE $(AMR_CFLAGS)
+CFLAGS+=$(AMR_CFLAGS)
 
 OBJS= bitstream.o \
       utils.o \
diff --git a/libavformat/Makefile b/libavformat/Makefile
index 00048892ee947578da4473e6de392af929c57548..4cebcf865df1dd8f3d5b45bc4ed82db0e7f8261c 100644
--- a/libavformat/Makefile
+++ b/libavformat/Makefile
@@ -4,9 +4,7 @@
 #
 include ../config.mak
 
-CFLAGS=-I$(BUILD_ROOT) -I$(SRC_PATH) -I$(SRC_PATH)/libavutil -I$(SRC_PATH)/libavcodec \
-       $(OPTFLAGS) -DHAVE_AV_CONFIG_H -D_FILE_OFFSET_BITS=64 \
-       -D_LARGEFILE_SOURCE -D_ISOC9X_SOURCE
+CFLAGS+=-I$(SRC_PATH)/libavcodec
 
 OBJS= utils.o cutils.o os_support.o allformats.o
 
diff --git a/libavutil/Makefile b/libavutil/Makefile
index b46c6271c07f0c0c78264270eb57ecfce7169bcc..2427a705cd41928dc7a461fd9ceebff649ceebe3 100644
--- a/libavutil/Makefile
+++ b/libavutil/Makefile
@@ -3,8 +3,7 @@
 #
 include ../config.mak
 
-CFLAGS=-DHAVE_AV_CONFIG_H -DBUILD_AVUTIL -I$(BUILD_ROOT) $(OPTFLAGS) \
-       -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_ISOC9X_SOURCE
+CFLAGS+=-DBUILD_AVUTIL
 
 OBJS= mathematics.o \
       rational.o \
diff --git a/libpostproc/Makefile b/libpostproc/Makefile
index f7619c31feb480c285053a7a5c802dbda96a2436..6f95049a3bbccab2eb0ecb8a943b6e4a51ee6968 100644
--- a/libpostproc/Makefile
+++ b/libpostproc/Makefile
@@ -15,8 +15,6 @@ SHARED_OBJS=postprocess_pic.o
 
 HEADERS = postprocess.h
 
-CFLAGS  = -I$(BUILD_ROOT) -I$(SRC_PATH)/libavutil $(OPTFLAGS)
-
 include $(SRC_PATH)/common.mak
 
 depend: postprocess.c