diff --git a/programs/fuzz/common.h b/programs/fuzz/common.h
index 094383c..88dceac 100644
--- a/programs/fuzz/common.h
+++ b/programs/fuzz/common.h
@@ -23,3 +23,6 @@
 int dummy_entropy(void *data, unsigned char *output, size_t len);
 int fuzz_recv_timeout(void *ctx, unsigned char *buf, size_t len,
                       uint32_t timeout);
+
+/* Implemented in the fuzz_*.c sources and required by onefile.c */
+int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size);
diff --git a/programs/fuzz/fuzz_pkcs7.c b/programs/fuzz/fuzz_pkcs7.c
index 2056913..38b4dc1 100644
--- a/programs/fuzz/fuzz_pkcs7.c
+++ b/programs/fuzz/fuzz_pkcs7.c
@@ -1,5 +1,6 @@
 #include <stdint.h>
 #include "mbedtls/pkcs7.h"
+#include "common.h"
 
 int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size)
 {
diff --git a/programs/fuzz/fuzz_pubkey.c b/programs/fuzz/fuzz_pubkey.c
index 0b153b1..b2500e5 100644
--- a/programs/fuzz/fuzz_pubkey.c
+++ b/programs/fuzz/fuzz_pubkey.c
@@ -1,6 +1,7 @@
 #include <stdint.h>
 #include <stdlib.h>
 #include "mbedtls/pk.h"
+#include "common.h"
 
 int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size)
 {
diff --git a/programs/fuzz/fuzz_x509crl.c b/programs/fuzz/fuzz_x509crl.c
index 151db92..e8dacd9 100644
--- a/programs/fuzz/fuzz_x509crl.c
+++ b/programs/fuzz/fuzz_x509crl.c
@@ -1,5 +1,6 @@
 #include <stdint.h>
 #include "mbedtls/x509_crl.h"
+#include "common.h"
 
 int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size)
 {
diff --git a/programs/fuzz/fuzz_x509crt.c b/programs/fuzz/fuzz_x509crt.c
index 3eee072..74d3b07 100644
--- a/programs/fuzz/fuzz_x509crt.c
+++ b/programs/fuzz/fuzz_x509crt.c
@@ -1,5 +1,6 @@
 #include <stdint.h>
 #include "mbedtls/x509_crt.h"
+#include "common.h"
 
 int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size)
 {
diff --git a/programs/fuzz/fuzz_x509csr.c b/programs/fuzz/fuzz_x509csr.c
index 7946e57..4c123f8 100644
--- a/programs/fuzz/fuzz_x509csr.c
+++ b/programs/fuzz/fuzz_x509csr.c
@@ -1,5 +1,6 @@
 #include <stdint.h>
 #include "mbedtls/x509_csr.h"
+#include "common.h"
 
 int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size)
 {
diff --git a/programs/fuzz/onefile.c b/programs/fuzz/onefile.c
index 3b2709f..2d4330a 100644
--- a/programs/fuzz/onefile.c
+++ b/programs/fuzz/onefile.c
@@ -1,14 +1,13 @@
 #include <stdint.h>
 #include <stdlib.h>
 #include <stdio.h>
+#include "common.h"
 
 /* This file doesn't use any Mbed TLS function, but grab mbedtls_config.h anyway
  * in case it contains platform-specific #defines related to malloc or
  * stdio functions. */
 #include "mbedtls/build_info.h"
 
-int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size);
-
 int main(int argc, char **argv)
 {
     FILE *fp;