Index: libcfa/prelude/Makefile.am
===================================================================
--- libcfa/prelude/Makefile.am	(revision 250583e1d4182a47696d102674000af3f44b3644)
+++ libcfa/prelude/Makefile.am	(revision 850aff17345d3e7433f854ef3f1b65369f8016d8)
@@ -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@
 
Index: libcfa/src/Makefile.am
===================================================================
--- libcfa/src/Makefile.am	(revision 250583e1d4182a47696d102674000af3f44b3644)
+++ libcfa/src/Makefile.am	(revision 850aff17345d3e7433f854ef3f1b65369f8016d8)
@@ -33,6 +33,6 @@
 # The built sources must not depend on the installed inst_headers_src
 AM_CFAFLAGS = -quiet -cfalib -I$(srcdir)/stdhdr -I$(srcdir)/concurrency $(if $(findstring ${gdbwaittarget}, ${@}), -XCFA --gdb) @CONFIG_CFAFLAGS@
-AM_CFLAGS = -g -Wall -Wno-unused-function -fPIC -fexceptions -pthread @ARCH_FLAGS@ @CONFIG_CFLAGS@
-AM_CCASFLAGS = -g -Wall -Wno-unused-function @ARCH_FLAGS@ @CONFIG_CFLAGS@
+AM_CFLAGS = -g -Wall -Werror=return-type -Wno-unused-function -fPIC -fexceptions -pthread @ARCH_FLAGS@ @CONFIG_CFLAGS@
+AM_CCASFLAGS = -g -Wall -Werror=return-type -Wno-unused-function @ARCH_FLAGS@ @CONFIG_CFLAGS@
 CFACC = @CFACC@