diff --git a/Makefile b/Makefile
index 57c82b3..93a1aba 100644
--- a/Makefile
+++ b/Makefile
@@ -83,6 +83,13 @@ TMPDIR ?= /tmp
 export CFLAGS	= $(call PKGCFG,cflags)
 export CXXFLAGS = $(call PKGCFG,cxxflags)
 
+ifeq ($(CFLAGS),)
+$(error CFLAGS not set)
+endif
+ifeq ($(CXXFLAGS),)
+$(error CXXFLAGS not set)
+endif
+
 ### The version number of VDR's plugin API:
 
 APIVERSION = $(call PKGCFG,apiversion)