diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 0496bcd..c1cca40 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -194,9 +194,9 @@
             echo "TEST=unittests"
           fi
           if ${{ contains(matrix.extra, 'asan') }}; then
-            echo "SANITIZER_CFLAGS=-g -O1 -DABORT_ON_INTERNAL_ERROR -DEXITFREE -fsanitize-recover=all -fsanitize=address -fsanitize=undefined -fno-omit-frame-pointer"
-            echo "ASAN_OPTIONS=print_stacktrace=1 log_path=${LOG_DIR}/asan"
-            echo "UBSAN_OPTIONS=print_stacktrace=1 log_path=${LOG_DIR}/ubsan"
+            echo "SANITIZER_CFLAGS=-g -O0 -DABORT_ON_INTERNAL_ERROR -DEXITFREE -fsanitize-recover=all -fsanitize=address -fsanitize=undefined -fno-omit-frame-pointer"
+            echo "ASAN_OPTIONS=print_stacktrace=1:log_path=${LOG_DIR}/asan"
+            echo "UBSAN_OPTIONS=print_stacktrace=1:log_path=${LOG_DIR}/ubsan"
             echo "LSAN_OPTIONS=suppressions=${GITHUB_WORKSPACE}/src/testdir/lsan-suppress.txt"
           fi
           if ${{ contains(matrix.extra, 'vimtags') }}; then
@@ -304,6 +304,7 @@
         if: contains(matrix.extra, 'asan') && !cancelled()
         run: |
           for f in $(grep -lR '#[[:digit:]]* *0x[[:xdigit:]]*' "${LOG_DIR}"); do
+            echo "$f"
             asan_symbolize -l "$f"
             false # in order to fail a job
           done
diff --git a/src/testdir/Makefile b/src/testdir/Makefile
index 3b665e7..4c7a273 100644
--- a/src/testdir/Makefile
+++ b/src/testdir/Makefile
@@ -60,6 +60,9 @@
 
 $(SCRIPTS_TINY_OUT) $(NEW_TESTS_RES): $(VIMPROG)
 
+# For $ASAN_OPTIONS and $UBSAN_OPTIONS append the testname to it.
+# This assumes $ASAN_OPTIONS contains log_path as last part of the environment variable
+# For Github CI, those variables are set in .github/workflows/ci.yml
 
 # Execute an individual new style test, e.g.:
 # 	make test_largefile
@@ -114,7 +117,11 @@
 	@# 200 msec is sufficient, but only modern sleep supports a fraction of
 	@# a second, fall back to a second if it fails.
 	@-/bin/sh -c "sleep .2 > /dev/null 2>&1 || sleep 1"
-	$(RUN_VIMPROG) $*.in $(REDIR_TEST_TO_NULL)
+	if test -n "$${ASAN_OPTIONS}"; then \
+		ASAN_OPTIONS="$${ASAN_OPTIONS}_$*" UBSAN_OPTIONS="$${UBSAN_OPTIONS}_$*" $(RUN_VIMPROG) $*.in $(REDIR_TEST_TO_NULL) ; \
+	else \
+		$(RUN_VIMPROG) $*.in $(REDIR_TEST_TO_NULL) ; \
+	fi
 
 	@# Check if the test.out file matches test.ok.
 	@/bin/sh -c "if test -f test.out; then \
@@ -145,32 +152,53 @@
 .vim.res:
 	@echo "$(VIMPROG)" > vimcmd
 	@echo "$(RUN_VIMTEST)" >> vimcmd
-	$(RUN_VIMTEST) $(NO_INITS) -S runtest.vim $*.vim $(REDIR_TEST_TO_NULL)
+	if test -n "$${ASAN_OPTIONS}"; then \
+		ASAN_OPTIONS="$${ASAN_OPTIONS}_$*" UBSAN_OPTIONS="$${UBSAN_OPTIONS}_$*" $(RUN_VIMTEST) $(NO_INITS) -S runtest.vim $*.vim $(REDIR_TEST_TO_NULL) ; \
+	else \
+		$(RUN_VIMTEST) $(NO_INITS) -S runtest.vim $*.vim $(REDIR_TEST_TO_NULL) ; \
+	fi
 	@rm vimcmd
 
 test_gui.res: test_gui.vim
 	@echo "$(VIMPROG)" > vimcmd
 	@echo "$(RUN_GVIMTEST)" >> vimcmd
-	$(RUN_VIMTEST) -u NONE $(NO_INITS) -S runtest.vim $<
+	if test -n "$${ASAN_OPTIONS}"; then \
+		ASAN_OPTIONS="$${ASAN_OPTIONS}_$*" UBSAN_OPTIONS="$${UBSAN_OPTIONS}_$*" $(RUN_VIMTEST) -u NONE $(NO_INITS) -S runtest.vim $< ; \
+	else \
+		$(RUN_VIMTEST) -u NONE $(NO_INITS) -S runtest.vim $< ; \
+	fi
+
 	@rm vimcmd
 
 test_gui_init.res: test_gui_init.vim
 	@echo "$(VIMPROG)" > vimcmd
 	@echo "$(RUN_GVIMTEST_WITH_GVIMRC)" >> vimcmd
-	$(RUN_VIMTEST) -u gui_preinit.vim -U gui_init.vim $(NO_PLUGINS) -S runtest.vim $<
+	if test -n "$${ASAN_OPTIONS}"; then \
+		ASAN_OPTIONS="$${ASAN_OPTIONS}_$*" UBSAN_OPTIONS="$${UBSAN_OPTIONS}_$*" $(RUN_VIMTEST) -u gui_preinit.vim -U gui_init.vim $(NO_PLUGINS) -S runtest.vim $< ; \
+	else \
+		$(RUN_VIMTEST) -u gui_preinit.vim -U gui_init.vim $(NO_PLUGINS) -S runtest.vim $< ; \
+	fi
 	@rm vimcmd
 
 GEN_OPT_DEPS = gen_opt_test.vim ../optiondefs.h ../../runtime/doc/options.txt
 
 opt_test.vim: $(GEN_OPT_DEPS)
-	$(VIMPROG) -e -s -u NONE $(NO_INITS) --nofork --gui-dialog-file guidialog -S $(GEN_OPT_DEPS)
+	if test -n "$${ASAN_OPTIONS}"; then \
+		ASAN_OPTIONS="$${ASAN_OPTIONS}_$*" UBSAN_OPTIONS="$${UBSAN_OPTIONS}_$*" $(VIMPROG) -e -s -u NONE $(NO_INITS) --nofork --gui-dialog-file guidialog -S $(GEN_OPT_DEPS) ; \
+	else \
+		$(VIMPROG) -e -s -u NONE $(NO_INITS) --nofork --gui-dialog-file guidialog -S $(GEN_OPT_DEPS) ; \
+	fi
 	@if test -f test.log; then \
 		cat test.log; \
 		exit 1; \
 	fi
 
 test_xxd.res:
-	XXD=$(XXDPROG); export XXD; $(RUN_VIMTEST) $(NO_INITS) -S runtest.vim test_xxd.vim
+	if test -n "$${ASAN_OPTIONS}"; then \
+		XXD=$(XXDPROG); export XXD; ASAN_OPTIONS="$${ASAN_OPTIONS}_$*" UBSAN_OPTIONS="$${UBSAN_OPTIONS}_$*" $(RUN_VIMTEST) $(NO_INITS) -S runtest.vim test_xxd.vim ; \
+	else \
+		XXD=$(XXDPROG); export XXD; $(RUN_VIMTEST) $(NO_INITS) -S runtest.vim test_xxd.vim ; \
+	fi
 
 test_bench_regexp.res: test_bench_regexp.vim
 	-rm -rf benchmark.out $(RM_ON_RUN)
@@ -178,5 +206,9 @@
 	@# 200 msec is sufficient, but only modern sleep supports a fraction of
 	@# a second, fall back to a second if it fails.
 	@-/bin/sh -c "sleep .2 > /dev/null 2>&1 || sleep 1"
-	$(RUN_VIMTEST) $(NO_INITS) -S runtest.vim $*.vim $(REDIR_TEST_TO_NULL)
+	if test -n "$${ASAN_OPTIONS}"; then \
+		ASAN_OPTIONS="$${ASAN_OPTIONS}_$*" UBSAN_OPTIONS="$${UBSAN_OPTIONS}_$*" $(RUN_VIMTEST) $(NO_INITS) -S runtest.vim $*.vim $(REDIR_TEST_TO_NULL) ; \
+	else \
+		$(RUN_VIMTEST) $(NO_INITS) -S runtest.vim $*.vim $(REDIR_TEST_TO_NULL) ; \
+	fi
 	@/bin/sh -c "if test -f benchmark.out; then cat benchmark.out; fi"
diff --git a/src/version.c b/src/version.c
index 3931067..4831281 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    816,
+/**/
     815,
 /**/
     814,