diff --git a/src/seeder/util.cpp b/src/seeder/util.cpp
index 466ec7892f..6792183ced 100644
--- a/src/seeder/util.cpp
+++ b/src/seeder/util.cpp
@@ -1,24 +1,24 @@
 #include "util.h"
 
 #include <cstdio>
 
-std::string vstrprintf(const std::string &format, va_list ap) {
+std::string vstrprintf(const char *format, va_list ap) {
     char buffer[50000];
     char *p = buffer;
     int limit = sizeof(buffer);
     int ret;
     loop {
         va_list arg_ptr;
         va_copy(arg_ptr, ap);
-        ret = vsnprintf(p, limit, format.c_str(), arg_ptr);
+        ret = vsnprintf(p, limit, format, arg_ptr);
         va_end(arg_ptr);
         if (ret >= 0 && ret < limit) break;
         if (p != buffer) delete[] p;
         limit *= 2;
         p = new char[limit];
         if (p == nullptr) throw std::bad_alloc();
     }
     std::string str(p, p + ret);
     if (p != buffer) delete[] p;
     return str;
 }
diff --git a/src/seeder/util.h b/src/seeder/util.h
index fcebac2264..220ea11430 100644
--- a/src/seeder/util.h
+++ b/src/seeder/util.h
@@ -1,70 +1,70 @@
 #ifndef BITCOIN_SEEDER_UTIL_H
 #define BITCOIN_SEEDER_UTIL_H
 
 #include <cstdarg>
 #include <errno.h>
 #include <openssl/sha.h>
 #include <pthread.h>
 
 #include "uint256.h"
 
 #define loop for (;;)
 #define BEGIN(a) ((char *)&(a))
 #define END(a) ((char *)&((&(a))[1]))
 #define UBEGIN(a) ((uint8_t *)&(a))
 #define UEND(a) ((uint8_t *)&((&(a))[1]))
 #define ARRAYLEN(array) (sizeof(array) / sizeof((array)[0]))
 
 #define WSAGetLastError() errno
 #define WSAEINVAL EINVAL
 #define WSAEALREADY EALREADY
 #define WSAEWOULDBLOCK EWOULDBLOCK
 #define WSAEMSGSIZE EMSGSIZE
 #define WSAEINTR EINTR
 #define WSAEINPROGRESS EINPROGRESS
 #define WSAEADDRINUSE EADDRINUSE
 #define WSAENOTSOCK EBADF
 #define INVALID_SOCKET (SOCKET)(~0)
 #define SOCKET_ERROR -1
 
 template <typename T1> inline uint256 Hash(const T1 pbegin, const T1 pend) {
     static uint8_t pblank[1];
     uint256 hash1;
     SHA256((pbegin == pend ? pblank : (uint8_t *)&pbegin[0]),
            (pend - pbegin) * sizeof(pbegin[0]), (uint8_t *)&hash1);
     uint256 hash2;
     SHA256((uint8_t *)&hash1, sizeof(hash1), (uint8_t *)&hash2);
     return hash2;
 }
 
 static inline void Sleep(int nMilliSec) {
     struct timespec wa;
     wa.tv_sec = nMilliSec / 1000;
     wa.tv_nsec = (nMilliSec % 1000) * 1000000;
     nanosleep(&wa, nullptr);
 }
 
-std::string vstrprintf(const std::string &format, va_list ap);
+std::string vstrprintf(const char *format, va_list ap);
 
-static inline std::string strprintf(const std::string &format, ...) {
+static inline std::string strprintf(const char *format, ...) {
     va_list arg_ptr;
     va_start(arg_ptr, format);
     std::string ret = vstrprintf(format, arg_ptr);
     va_end(arg_ptr);
     return ret;
 }
 
 static inline bool error(std::string err, ...) {
     return false;
 }
 
 static inline bool my_printf(std::string err, ...) {
     return true;
 }
 
 std::vector<uint8_t> DecodeBase32(const char *p, bool *pfInvalid = nullptr);
 std::string DecodeBase32(const std::string &str);
 std::string EncodeBase32(const uint8_t *pch, size_t len);
 std::string EncodeBase32(const std::string &str);
 
 #endif