diff --git a/trunk/research/librtmp/Makefile b/trunk/research/librtmp/Makefile
index 0370dcb77..ca3e4734b 100755
--- a/trunk/research/librtmp/Makefile
+++ b/trunk/research/librtmp/Makefile
@@ -65,7 +65,7 @@ ifeq ($(GCC), arm-linux-gnueabi-gcc)
 endif
 # for mips, add -lgcc_eh, or stl compile failed.
 ifeq ($(GCC), mipsel-openwrt-linux-gcc)
-    EXTRA_CXX_FLAG = -g -O0 -ldl -lstdc++ -lgcc_eh
+    EXTRA_CXX_FLAG = -g -O0 -ldl -lstdc++ -lm -lgcc_eh
 endif
 # for ssl or nossl
 ifeq ($(HANDSHAKE), SSL)