diff --git a/src/error-demo/local.mk b/src/error-demo/local.mk
index 2cb2a0dc4..2c528490a 100644
--- a/src/error-demo/local.mk
+++ b/src/error-demo/local.mk
@@ -5,6 +5,8 @@ error-demo_DIR := $(d)
 error-demo_SOURCES := \
   $(wildcard $(d)/*.cc) \
 
+error-demo_CXXFLAGS += -I src/libutil -I src/libexpr
+
 error-demo_LIBS = libutil libexpr
 
 error-demo_LDFLAGS = -pthread $(SODIUM_LIBS) $(EDITLINE_LIBS) $(BOOST_LDFLAGS) -lboost_context -lboost_thread -lboost_system