Index: libcfa/prelude/Makefile.am
===================================================================
--- libcfa/prelude/Makefile.am	(revision f520c4c11c7c750ed2b2f4332c6c9909d4ea216d)
+++ libcfa/prelude/Makefile.am	(revision 891f7074e4bf1a3467ca38add7c71ff492fc38a0)
@@ -26,5 +26,5 @@
 
 CC = @LOCAL_CFACC@
-AM_CFLAGS = -g -Wall -Wno-unused-function -fPIC @ARCH_FLAGS@ @CONFIG_CFLAGS@
+AM_CFLAGS = -g -Wall -Werror=return-type -Wno-unused-function -fPIC @ARCH_FLAGS@ @CONFIG_CFLAGS@
 AM_CFAFLAGS = @CONFIG_CFAFLAGS@