diff --git a/qrexec/Makefile b/qrexec/Makefile
index 96c9c78..f6e905a 100644
--- a/qrexec/Makefile
+++ b/qrexec/Makefile
@@ -1,7 +1,7 @@
-CC=gcc
-CFLAGS+=-I. -g -O2 -Wall -Wextra -Werror -pie -fPIC `pkg-config --cflags vchan-$(BACKEND_VMM)`
-LDFLAGS=-pie
-LDLIBS=`pkg-config --libs vchan-$(BACKEND_VMM)` -lqrexec-utils
+CC ?= gcc
+CFLAGS += -I. -g -O2 -Wall -Wextra -Werror -pie -fPIC `pkg-config --cflags vchan-$(BACKEND_VMM)`
+LDFLAGS += -pie
+LDLIBS = `pkg-config --libs vchan-$(BACKEND_VMM)` -lqrexec-utils
 
 all: qrexec-agent qrexec-client-vm qrexec-fork-server
 qrexec-agent: qrexec-agent.o qrexec-agent-data.o
diff --git a/rpm_spec/core-vm.spec b/rpm_spec/core-vm.spec
index a23a200..0e42bd3 100644
--- a/rpm_spec/core-vm.spec
+++ b/rpm_spec/core-vm.spec
@@ -205,6 +205,7 @@ ln -sf . %{name}-%{version}
 %setup -T -D
 
 %build
+%{?set_build_flags}
 for dir in qubes-rpc qrexec misc; do
   (cd $dir; make)
 done