diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 33a40325..9349580e 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -256,7 +256,8 @@ jobs:
       - name: build
         run: |
           make
-          make -C tests/oss-fuzz -f Makefile.ci check clean
+          make  EXTRA_CFLAGS=-Werror -C tests/oss-fuzz -f Makefile.ci check clean
+
   documentation:
     runs-on: ubuntu-latest
     steps:
diff --git a/configure.ac b/configure.ac
index aa02d3eb..8a5e37f7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1573,9 +1573,10 @@ else
 fi
 
 mkdir -p include/coap$LIBCOAP_API_VERSION
-head -19 cmake_coap_defines.h.in > include/coap$LIBCOAP_API_VERSION/coap_defines.h
+DIR=`dirname $0`
+head -19 $DIR/cmake_coap_defines.h.in > include/coap$LIBCOAP_API_VERSION/coap_defines.h
 LT_TEMP=`grep -B2 " COAP_" coap_config.h >> include/coap$LIBCOAP_API_VERSION/coap_defines.h`
-tail -2 cmake_coap_defines.h.in >> include/coap$LIBCOAP_API_VERSION/coap_defines.h
+tail -2 $DIR/cmake_coap_defines.h.in >> include/coap$LIBCOAP_API_VERSION/coap_defines.h
 if test "x$LT_TEMP" != "x" ; then
     AC_MSG_ERROR([Unable to build coap_defines.h])
 fi
diff --git a/tests/oss-fuzz/Makefile.ci.in b/tests/oss-fuzz/Makefile.ci.in
index 07016b01..e4a2b202 100644
--- a/tests/oss-fuzz/Makefile.ci.in
+++ b/tests/oss-fuzz/Makefile.ci.in
@@ -27,7 +27,7 @@ PROGRAMS:=$(patsubst %_target.o, %_fuzzer, $(OBJECTS))
 all: $(PROGRAMS)
 
 $(OUT)/%.o: %.c
-	$(CC) $(CPPFLAGS) $(CFLAGS) -c $^ -o $@
+	$(CC) $(CPPFLAGS) $(CFLAGS) $(EXTRA_CFLAGS) -c $^ -o $@
 
 %_fuzzer: %_target.o
 	$(LINK.cc) $(CXXFLAGS) $^ $(top_builddir)/.libs/$(libcoap).a $(LDFLAGS) $(LDLIBS) $(DTLS_LIBS) -o $@
@@ -35,4 +35,4 @@ $(OUT)/%.o: %.c
 check: $(OBJECTS)
 
 clean:
-	@-$(RM) $(OBJECTS) $(PROGRAMS)
+	@-$(RM) -f $(OBJECTS) $(PROGRAMS)