diff --git a/libafl_targets/src/libfuzzer.c b/libafl_targets/src/libfuzzer.c
index ff6e2968ee..70df4f1132 100644
--- a/libafl_targets/src/libfuzzer.c
+++ b/libafl_targets/src/libfuzzer.c
@@ -1,5 +1,8 @@
 #include "common.h"
 #include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
+
 #ifdef __APPLE__
   #include <malloc/malloc.h>
 #else
@@ -18,6 +21,8 @@ EXT_FUNC(LLVMFuzzerCustomCrossOver, size_t,
          false);
 EXT_FUNC_IMPL(LLVMFuzzerTestOneInput, int, (const uint8_t *Data, size_t Size),
               false) {
+  fprintf(stderr, "Weakly defined \"LLVMFuzzerTestOneInput\" is linked. Did you add extern \"C\" to your harness?\n");
+  abort();
   return 0;
 }
 
diff --git a/scripts/fmt_all.sh b/scripts/fmt_all.sh
index 8bd22275cb..5119c53477 100755
--- a/scripts/fmt_all.sh
+++ b/scripts/fmt_all.sh
@@ -4,7 +4,7 @@ SCRIPT_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )"
 LIBAFL_DIR=$(realpath "$SCRIPT_DIR/..")
 
 if [ "$1" = "check" ]; then
-  cargo run --manifest-path "$LIBAFL_DIR/utils/libafl_fmt/Cargo.toml" --release -- -c
+  cargo run --manifest-path "$LIBAFL_DIR/utils/libafl_fmt/Cargo.toml" --release -- -c --verbose
 else
-  cargo run --manifest-path "$LIBAFL_DIR/utils/libafl_fmt/Cargo.toml" --release
+  cargo run --manifest-path "$LIBAFL_DIR/utils/libafl_fmt/Cargo.toml" --release -- --verbose
 fi
diff --git a/utils/libafl_fmt/src/main.rs b/utils/libafl_fmt/src/main.rs
index 0e85fde97b..f2f480f8f1 100644
--- a/utils/libafl_fmt/src/main.rs
+++ b/utils/libafl_fmt/src/main.rs
@@ -31,7 +31,7 @@ async fn run_cargo_fmt(path: PathBuf, is_check: bool, verbose: bool) -> io::Resu
     let res = fmt_command.output().await?;
 
     if !res.status.success() {
-        println!("{}", from_utf8(&res.stdout).unwrap());
+        println!("{}", from_utf8(&res.stderr).unwrap());
         return Err(io::Error::new(ErrorKind::Other, "Cargo fmt failed."));
     }
 
@@ -96,6 +96,7 @@ async fn main() -> io::Result<()> {
         r".*utils/gdb_qemu.*",
         r".*docs/listings/baby_fuzzer/listing-.*",
         r".*LibAFL/Cargo.toml.*",
+        r".*AFLplusplus.*",
     ])
     .expect("Could not create the regex set from the given regex");
 
@@ -105,6 +106,7 @@ async fn main() -> io::Result<()> {
         r".*stb_image\.h$",
         r".*dlmalloc\.c$",
         r".*QEMU-Nyx.*",
+        r".*AFLplusplus.*",
     ])
     .expect("Could not create the regex set from the given regex");