diff --git a/.clusterfuzzlite/build.sh b/.clusterfuzzlite/build.sh
index 6bb324cc..47728c2f 100755
--- a/.clusterfuzzlite/build.sh
+++ b/.clusterfuzzlite/build.sh
@@ -1,7 +1,7 @@
 #!/bin/bash -eu
 
 # build project
-cmake -S . -B build -DCMAKE_BUILD_TYPE=Release -DCLUSTERFUZZ=ON
+cmake -S . -B build -DCMAKE_BUILD_TYPE=DEBUG -DCLUSTERFUZZ=ON
 cmake --build build
 
 # copy binary and dict to $OUT
diff --git a/CMakeLists.txt b/CMakeLists.txt
index a90fc8f7..418997f1 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -409,7 +409,7 @@ if(CLUSTERFUZZ)
 	add_subdirectory(regress/parser-libfuzzer)
 	if (NOT DEFINED ENV{CLUSTERFUZZLITE})
 		set(CMAKE_C_COMPILER clang)
-		string(APPEND CMAKE_C_FLAGS " -g -O1 -fsanitize=fuzzer-no-link")
+		string(APPEND CMAKE_C_FLAGS " -g -O0 -fsanitize=fuzzer-no-link")
 	endif()
 endif()
 add_subdirectory(compat)
diff --git a/iked/ikev2_pld.c b/iked/ikev2_pld.c
index 05ed27a0..104f9de4 100644
--- a/iked/ikev2_pld.c
+++ b/iked/ikev2_pld.c
@@ -18,6 +18,7 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+#include <stdint.h>
 #include <sys/queue.h>
 #include <sys/socket.h>
 #include <sys/uio.h>
diff --git a/regress/parser-libfuzzer/common.c b/regress/parser-libfuzzer/common.c
index 7871d208..2030e75e 100644
--- a/regress/parser-libfuzzer/common.c
+++ b/regress/parser-libfuzzer/common.c
@@ -12,6 +12,7 @@
 
 #include <event.h>
 #include <limits.h>
+#include <string.h>
 
 #include "iked.h"
 #include "types.h"
@@ -162,6 +163,7 @@ ssize_t
 ikev2_nat_detection(struct iked *env, struct iked_message *msg,
     void *ptr, size_t len, u_int type, int frompeer)
 {
+	bzero(ptr, len);
 	return (0);
 }
 
diff --git a/regress/parser-libfuzzer/run_test.sh b/regress/parser-libfuzzer/run_test.sh
index 9560e07d..31ad4552 100644
--- a/regress/parser-libfuzzer/run_test.sh
+++ b/regress/parser-libfuzzer/run_test.sh
@@ -1,6 +1,7 @@
 #!/bin/sh
 
 # script to run the parser-fuzzer for 5 minutes with the right options
+# use repo github.com/openiked-portable/corpus as corpus for faster results
 
 # ASAN-option to help finding the source of memory leaks
 export ASAN_OPTIONS=fast_unwind_on_malloc=0