diff --git a/include/mosquitto/libcommon_file.h b/include/mosquitto/libcommon_file.h
index 35633852..719dc3be 100644
--- a/include/mosquitto/libcommon_file.h
+++ b/include/mosquitto/libcommon_file.h
@@ -51,7 +51,7 @@ libmosqcommon_EXPORT int mosquitto_write_file(const char* target_path, bool rest
 /*
  * Function: mosquitto_read_file
  */
-libmosqcommon_EXPORT int mosquitto_read_file(const char *file, char **buf);
+libmosqcommon_EXPORT int mosquitto_read_file(const char *file, char **buf, size_t *buflen);
 
 
 /*
diff --git a/libcommon/file_common.c b/libcommon/file_common.c
index 1fa2b2dd..80847a23 100644
--- a/libcommon/file_common.c
+++ b/libcommon/file_common.c
@@ -432,11 +432,11 @@ error:
 }
 
 
-int mosquitto_read_file(const char *file, char **buf)
+int mosquitto_read_file(const char *file, char **buf, size_t *buflen)
 {
 	FILE *fptr;
-	size_t buflen;
 	long l;
+	size_t buflen_i;
 
 	*buf = NULL;
 	fptr = fopen(file, "rt");
@@ -449,24 +449,27 @@ int mosquitto_read_file(const char *file, char **buf)
 		fclose(fptr);
 		return MOSQ_ERR_ERRNO;
 	}
-	buflen = (size_t)l;
+	buflen_i = (size_t)l;
 
-	if(buflen == 0){
+	if(buflen_i == 0){
 		fclose(fptr);
 		return MOSQ_ERR_SUCCESS;
 	}
 
-	*buf = mosquitto_calloc(buflen+1, sizeof(char));
+	*buf = mosquitto_calloc(buflen_i+1, sizeof(char));
 	if((*buf) == NULL){
 		fclose(fptr);
 		return MOSQ_ERR_NOMEM;
 	}
-	if(fread(*buf, 1, buflen, fptr) != buflen){
+	if(fread(*buf, 1, buflen_i, fptr) != buflen_i){
 		free(*buf);
 		fclose(fptr);
 		return MOSQ_ERR_INVAL;
 	}
 	fclose(fptr);
+	if(buflen){
+		*buflen = buflen_i;
+	}
 
 	return MOSQ_ERR_SUCCESS;
 }
diff --git a/src/http_api.c b/src/http_api.c
index 00f78c84..5921cdbd 100644
--- a/src/http_api.c
+++ b/src/http_api.c
@@ -387,11 +387,11 @@ int http_api__start(struct mosquitto__listener *listener)
 	port = listener->port;
 
 	if(listener->certfile && listener->keyfile){
-		if(mosquitto_read_file(listener->certfile, &x509_cert)){
+		if(mosquitto_read_file(listener->certfile, &x509_cert, NULL)){
 			log__printf(NULL, MOSQ_LOG_ERR, "Error: Unable to load server certificate \"%s\". Check certfile.", listener->certfile);
 			return MOSQ_ERR_INVAL;
 		}
-		if(mosquitto_read_file(listener->keyfile, &x509_key)){
+		if(mosquitto_read_file(listener->keyfile, &x509_key, NULL)){
 			log__printf(NULL, MOSQ_LOG_ERR, "Error: Unable to load server key file \"%s\". Check keyfile.", listener->keyfile);
 			mosquitto_FREE(x509_cert);
 			return MOSQ_ERR_INVAL;