diff --git a/common/protocol/Makefile.am b/common/protocol/Makefile.am
index cfac2d8d3..778758209 100644
--- a/common/protocol/Makefile.am
+++ b/common/protocol/Makefile.am
@@ -34,7 +34,8 @@ noinst_LTLIBRARIES = libprotocol.la
 # warnings here.
 libprotocol_la_SOURCES = guestfs_protocol.c  guestfs_protocol.h
 libprotocol_la_CFLAGS = \
-	-Wall -Wno-unused -fno-strict-aliasing $(GCC_VISIBILITY_HIDDEN)
+	-Wall -Wno-unused -fno-strict-aliasing $(GCC_VISIBILITY_HIDDEN) \
+  $(RPC_CFLAGS)
 
 if HAVE_RPCGEN
 
diff --git a/fish/Makefile.am b/fish/Makefile.am
index a6efbb439..8623e8eca 100644
--- a/fish/Makefile.am
+++ b/fish/Makefile.am
@@ -101,7 +101,7 @@ guestfish_SOURCES = \
 # This convenience library is solely to compile its generated sources with
 # custom flags.
 librc_protocol_la_SOURCES = rc_protocol.c rc_protocol.h
-librc_protocol_la_CFLAGS = -Wall -Wno-unused -fno-strict-aliasing
+librc_protocol_la_CFLAGS = -Wall -Wno-unused -fno-strict-aliasing $(RPC_CFLAGS)
 
 # Build the command lookup perfect hash code.  The generated code has
 # lots of warnings so we must compile it in a separate mini-library.