diff --git a/src/modules/cdp/diameter.h b/src/modules/cdp/diameter.h
index 2be25258c04..5a7cb0e0c53 100644
--- a/src/modules/cdp/diameter.h
+++ b/src/modules/cdp/diameter.h
@@ -74,7 +74,7 @@
 
 #define set_4bytes(_b,_v) \
 	{(_b)[0]=((_v)&0xff000000)>>24;(_b)[1]=((_v)&0x00ff0000)>>16;\
-	(_b)[2]=((_v)&0x0000ff00)>>8;(_b)[3]=((_v)&0x000000ff);}
+	(_b)[2]=((_v)&0x0000ff00)>>8;(_b)[3]=(unsigned char)((_v)&0x000000ff);}
 
 #define to_32x_len( _len_ ) \
 	( (_len_)+(((_len_)&3)?4-((_len_)&3):0) )