diff --git a/scripts/afl-fuzz/.gitignore b/scripts/afl-fuzz/.gitignore
new file mode 100644
index 0000000..24c8d6c
--- /dev/null
+++ b/scripts/afl-fuzz/.gitignore
@@ -0,0 +1 @@
+*/fuzz
diff --git a/scripts/afl-fuzz/Makefile b/scripts/afl-fuzz/Makefile
index c819797..0fc87d5 100644
--- a/scripts/afl-fuzz/Makefile
+++ b/scripts/afl-fuzz/Makefile
@@ -1,7 +1,6 @@
 SRC := $(wildcard */*.c)
 EXE := $(SRC:.c=)
 
-CFLAGS := -O2 -s
 LDLIBS := -ldeflate
 LDFLAGS := -L../..
 CPPFLAGS := -I../..
diff --git a/scripts/afl-fuzz/deflate_compress/fuzz.c b/scripts/afl-fuzz/deflate_compress/fuzz.c
index d65d17e..6e6a3d9 100644
--- a/scripts/afl-fuzz/deflate_compress/fuzz.c
+++ b/scripts/afl-fuzz/deflate_compress/fuzz.c
@@ -12,15 +12,22 @@ int main(int argc, char **argv)
 	int ret;
 	int fd = open(argv[1], O_RDONLY);
 	struct stat stbuf;
+	unsigned char level;
 	assert(fd >= 0);
 	ret = fstat(fd, &stbuf);
 	assert(!ret);
 
-	char in[stbuf.st_size];
+	if (stbuf.st_size == 0)
+		return 0;
+	ret = read(fd, &level, 1);
+	assert(ret == 1);
+	level %= 13;
+
+	char in[stbuf.st_size - 1];
 	ret = read(fd, in, sizeof in);
 	assert(ret == sizeof in);
 
-	c = libdeflate_alloc_compressor(6);
+	c = libdeflate_alloc_compressor(level);
 	d = libdeflate_alloc_decompressor();
 
 	char out[sizeof(in)];
diff --git a/scripts/afl-fuzz/fuzz.sh b/scripts/afl-fuzz/fuzz.sh
new file mode 100755
index 0000000..405d7d1
--- /dev/null
+++ b/scripts/afl-fuzz/fuzz.sh
@@ -0,0 +1,148 @@
+#!/bin/bash
+
+set -e -u -o pipefail
+
+cd "$(dirname "$0")"
+
+read -r -a AVAILABLE_TARGETS < <(echo */fuzz.c | sed 's@/fuzz.c@@g')
+
+usage()
+{
+	cat << EOF
+Usage: $0 [OPTION]... [TARGET]...
+
+Fuzz libdeflate with afl-fuzz.
+
+Options:
+   --asan          Enable AddressSanitizer
+   --no-resume     Don't resume existing afl-fuzz session; start a new one
+   --ubsan         Enable UndefinedBehaviorSanitizer
+
+Available targets: ${AVAILABLE_TARGETS[*]}
+EOF
+}
+
+die()
+{
+	echo "$*" 1>&2
+	exit 1
+}
+
+asan=false
+ubsan=false
+may_resume=true
+
+longopts_array=(
+asan
+help
+no-resume
+ubsan
+)
+longopts=$(echo "${longopts_array[@]}" | tr ' ' ',')
+
+if ! options=$(getopt -o "" -l "$longopts" -- "$@"); then
+	usage 1>&2
+	exit 1
+fi
+eval set -- "$options"
+while (( $# >= 0 )); do
+	case "$1" in
+	--asan)
+		asan=true
+		;;
+	--help)
+		usage
+		exit 0
+		;;
+	--no-resume)
+		may_resume=false
+		;;
+	--ubsan)
+		ubsan=true
+		;;
+	--)
+		shift
+		break
+		;;
+	*)
+		echo 1>&2 "Invalid option: \"$1\""
+		usage 1>&2
+		exit 1
+	esac
+	shift
+done
+
+if $asan && $ubsan; then
+	die "--asan and --ubsan are mutually exclusive"
+fi
+
+if ! type -P afl-fuzz > /dev/null; then
+	die "afl-fuzz is not installed"
+fi
+
+if (( $# == 0 )); then
+	targets=("${AVAILABLE_TARGETS[@]}")
+else
+	for target; do
+		found=false
+		for t in "${AVAILABLE_TARGETS[@]}"; do
+			if [ "$target" = "$t" ]; then
+				found=true
+			fi
+		done
+		if ! $found; then
+			echo 1>&2 "Unknown target '$target'"
+			echo 1>&2 "Available targets: ${AVAILABLE_TARGETS[*]}"
+			exit 1
+		fi
+	done
+	targets=("$@")
+fi
+if (( ${#targets[@]} > 1 )) && ! type -P urxvt > /dev/null; then
+	die "urxvt is not installed"
+fi
+
+afl_opts=""
+if $asan; then
+	export AFL_USE_ASAN=1
+	export CFLAGS="-O2 -m32"
+	export CC=afl-clang
+	afl_opts+=" -m 800"
+elif $ubsan; then
+	export CFLAGS="-fsanitize=undefined -fno-sanitize-recover=undefined"
+	export CC=afl-gcc
+else
+	export AFL_HARDEN=1
+	export CFLAGS="-O2"
+	export CC=afl-clang-fast
+fi
+
+sudo sh -c "echo core > /proc/sys/kernel/core_pattern"
+sudo sh -c "echo performance | tee /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor"
+
+NPROC=$(getconf _NPROCESSORS_ONLN)
+
+make "-j$NPROC" -C ../../ libdeflate.a
+make "-j$NPROC" -B
+
+for dir in "${targets[@]}"; do
+	cp -vaT "$dir" "/tmp/$dir"
+	indir=/tmp/$dir/inputs
+	outdir=/tmp/$dir/outputs
+	if [ -e "$outdir" ]; then
+		if $may_resume; then
+			indir="-"
+		else
+			rm -rf "${outdir:?}"/*
+		fi
+	else
+		mkdir "$outdir"
+	fi
+	cmd="afl-fuzz -i $indir -o $outdir -T $dir $afl_opts -- /tmp/$dir/fuzz @@"
+	if (( ${#targets[@]} > 1 )); then
+		urxvt -e bash -c "$cmd" &
+	else
+		$cmd
+	fi
+done
+wait
diff --git a/scripts/afl-fuzz/prepare_for_fuzz.sh b/scripts/afl-fuzz/prepare_for_fuzz.sh
deleted file mode 100755
index 06911c1..0000000
--- a/scripts/afl-fuzz/prepare_for_fuzz.sh
+++ /dev/null
@@ -1,14 +0,0 @@
-#!/bin/sh
-
-set -e
-
-make -C ../../ clean
-make clean
-AFL_HARDEN=1 make CC=afl-gcc -C ../../
-AFL_HARDEN=1 make CC=afl-gcc
-
-for dir in $(find . -mindepth 1 -maxdepth 1 -type d); do
-	rm -rf /tmp/$dir
-	cp -va $dir /tmp/$dir
-	mkdir -p /tmp/$dir/outputs
-done