diff --git a/src/AbstractDiskWriter.cc b/src/AbstractDiskWriter.cc
index 0bd84248..55412927 100644
--- a/src/AbstractDiskWriter.cc
+++ b/src/AbstractDiskWriter.cc
@@ -166,7 +166,7 @@ void AbstractDiskWriter::closeFile()
 #if defined(__MINGW32__) || defined(_MSC_VER)
     CloseHandle(fd_);
 #else  // !__MINGW32__
-    close(fd_);
+    a2_close(fd_);
 #endif // !__MINGW32__
     fd_ = A2_BAD_FD;
   }
@@ -319,7 +319,7 @@ ssize_t AbstractDiskWriter::readDataInternal(unsigned char* data, size_t len,
     }
 #else  // !__MINGW32__
     ssize_t ret = 0;
-    while ((ret = read(fd_, data, len)) == -1 && errno == EINTR)
+    while ((ret = a2_read(fd_, data, len)) == -1 && errno == EINTR)
       ;
     return ret;
 #endif // !__MINGW32__
diff --git a/src/AppleTLSSession.cc b/src/AppleTLSSession.cc
index f4174a58..12bcb0e6 100644
--- a/src/AppleTLSSession.cc
+++ b/src/AppleTLSSession.cc
@@ -694,7 +694,7 @@ OSStatus AppleTLSSession::sockRead(void* data, size_t* len)
   uint8_t* buffer = static_cast<uint8_t*>(data);
   *len = 0;
   while (remain) {
-    ssize_t r = read(sockfd_, buffer, remain);
+    ssize_t r = a2_read(sockfd_, buffer, remain);
     if (r == 0) {
       return errSSLClosedGraceful;
     }
diff --git a/src/BufferedFile.cc b/src/BufferedFile.cc
index d1735bac..6ad21a59 100644
--- a/src/BufferedFile.cc
+++ b/src/BufferedFile.cc
@@ -53,12 +53,12 @@ BufferedFile::BufferedFile(const char* filename, const char* mode)
               a2fopen(filename, mode)
 #endif // !__MINGW32__
               ),
-      supportsColor_(fp_ ? isatty(fileno(fp_)) : false)
+      supportsColor_(fp_ ? a2_isatty(a2_fileno(fp_)) : false)
 {
 }
 
 BufferedFile::BufferedFile(FILE* fp)
-    : fp_(fp), supportsColor_(fp_ ? isatty(fileno(fp_)) : false)
+    : fp_(fp), supportsColor_(fp_ ? a2_isatty(a2_fileno(fp_)) : false)
 {
 }
 
@@ -82,9 +82,9 @@ int BufferedFile::onClose()
   if (fp_) {
     fflush(fp_);
 #if !defined(__MINGW32__) && !defined(_MSC_VER)
-    fsync(fileno(fp_));
+    fsync(a2_fileno(fp_));
 #else  // __MINGW32__
-    _commit(fileno(fp_));
+    _commit(a2_fileno(fp_));
 #endif // __MINGW32__
     rv = fclose(fp_);
     fp_ = nullptr;
diff --git a/src/ConsoleStatCalc.cc b/src/ConsoleStatCalc.cc
index 09a85ad5..b7fe8224 100644
--- a/src/ConsoleStatCalc.cc
+++ b/src/ConsoleStatCalc.cc
@@ -277,7 +277,7 @@ ConsoleStatCalc::ConsoleStatCalc(std::chrono::seconds summaryInterval,
 #if defined(__MINGW32__) || defined(_MSC_VER)
       isTTY_(true),
 #else  // !__MINGW32__
-      isTTY_(isatty(STDOUT_FILENO) == 1),
+      isTTY_(a2_isatty(STDOUT_FILENO) == 1),
 #endif // !__MINGW32__
       colorOutput_(colorOutput)
 {
diff --git a/src/EpollEventPoll.cc b/src/EpollEventPoll.cc
index 340400dd..c507bb42 100644
--- a/src/EpollEventPoll.cc
+++ b/src/EpollEventPoll.cc
@@ -91,7 +91,7 @@ EpollEventPoll::EpollEventPoll()
 EpollEventPoll::~EpollEventPoll()
 {
   if (epfd_ != -1) {
-    int r = close(epfd_);
+    int r = a2_close(epfd_);
     int errNum = errno;
     if (r == -1) {
       A2_LOG_ERROR(fmt("Error occurred while closing epoll file descriptor"
diff --git a/src/File.cc b/src/File.cc
index a9670634..a34e664c 100644
--- a/src/File.cc
+++ b/src/File.cc
@@ -55,11 +55,11 @@
 #include "fmt.h"
 
 #if defined(_MSC_VER)
-#  if !defined(S_ISREG) && defined(S_IFMT) && defined(S_IFREG)
-#    define S_ISREG(m) (((m) & S_IFMT) == S_IFREG)
+#  if !defined(S_ISREG) && defined(_S_IFMT) && defined(_S_IFREG)
+#    define S_ISREG(m) (((m) & _S_IFMT) == _S_IFREG)
 #  endif
-#  if !defined(S_ISDIR) && defined(S_IFMT) && defined(S_IFDIR)
-#    define S_ISDIR(m) (((m) & S_IFMT) == S_IFDIR)
+#  if !defined(S_ISDIR) && defined(_S_IFMT) && defined(_S_IFDIR)
+#    define S_ISDIR(m) (((m) & _S_IFMT) == _S_IFDIR)
 #  endif
 #endif
 
diff --git a/src/GZipFile.cc b/src/GZipFile.cc
index b85665d8..b2e23c34 100644
--- a/src/GZipFile.cc
+++ b/src/GZipFile.cc
@@ -57,7 +57,7 @@ GZipFile::GZipFile(const char* filename, const char* mode)
 #endif // !__MINGW32__
       ;
   if (fp) {
-    int fd = dup(fileno(fp));
+    int fd = a2_dup(a2_fileno(fp));
     if (fd != -1) {
       fp_ = gzdopen(fd, mode);
       if (fp_) {
@@ -70,7 +70,7 @@ GZipFile::GZipFile(const char* filename, const char* mode)
 #endif
       }
       else {
-        ::close(fd);
+        ::a2_close(fd);
       }
     }
     fclose(fp);
diff --git a/src/GenericParser.h b/src/GenericParser.h
index 7373b066..ace91e28 100644
--- a/src/GenericParser.h
+++ b/src/GenericParser.h
@@ -101,11 +101,11 @@ typename Parser::ResultType parseFile(Parser& parser,
   if (fd == -1) {
     return Parser::ParserStateMachineType::noResult();
   }
-  auto fdclose = defer(fd, close);
+  auto fdclose = defer(fd, a2_close);
   std::array<char, 4_k> buf;
   ssize_t nread;
   ssize_t nproc;
-  while ((nread = read(fd, buf.data(), buf.size())) > 0) {
+  while ((nread = a2_read(fd, buf.data(), buf.size())) > 0) {
     nproc = parser.parseUpdate(buf.data(), nread);
     if (nproc < 0) {
       break;
diff --git a/src/OptionParser.cc b/src/OptionParser.cc
index b4a66e75..63b5c4b4 100644
--- a/src/OptionParser.cc
+++ b/src/OptionParser.cc
@@ -198,7 +198,7 @@ void OptionParser::parseArg(std::ostream& out,
       // option is ambiguous.
       int ambiguous = 0;
       for (int i = 1, len = option::countOption(); i < len; ++i) {
-        PrefPtr pref = option::i2p(i);
+        PrefPtr pref = aria2::option::i2p(i);
         const OptionHandler* h = find(pref);
         if (h && !h->isHidden()) {
           if (strcmp(pref->k, optstr) == 0) {
diff --git a/src/PortEventPoll.cc b/src/PortEventPoll.cc
index ecd7fbfa..39f5a1fe 100644
--- a/src/PortEventPoll.cc
+++ b/src/PortEventPoll.cc
@@ -85,7 +85,7 @@ PortEventPoll::PortEventPoll()
 PortEventPoll::~PortEventPoll()
 {
   if (port_ != -1) {
-    int r = close(port_);
+    int r = a2_sclose(port_);
     int errNum = errno;
     if (r == -1) {
       A2_LOG_ERROR(fmt("Error occurred while closing port %d: %s", port_,
diff --git a/src/XmlParser.cc b/src/XmlParser.cc
index 15b273d7..4eb95c46 100644
--- a/src/XmlParser.cc
+++ b/src/XmlParser.cc
@@ -58,12 +58,12 @@ bool parseFile(const std::string& filename, ParserStateMachine* psm)
       return false;
     }
   }
-  auto fdclose = defer(fd, close);
+  auto fdclose = defer(fd, a2_close);
   XmlParser ps(psm);
   std::array<char, 4_k> buf;
   ssize_t nread;
   bool retval = true;
-  while ((nread = read(fd, buf.data(), buf.size())) > 0) {
+  while ((nread = a2_read(fd, buf.data(), buf.size())) > 0) {
     if (ps.parseUpdate(buf.data(), nread) < 0) {
       retval = false;
       break;
diff --git a/test/FileTest.cc b/test/FileTest.cc
index e4c2f01a..b3773d36 100644
--- a/test/FileTest.cc
+++ b/test/FileTest.cc
@@ -88,7 +88,7 @@ void FileTest::testRemove()
   if ((fd = creat(name.c_str(), S_IRUSR | S_IWUSR)) < 0) {
     CPPUNIT_FAIL("cannot create test file");
   }
-  close(fd);
+  a2_close(fd);
   File f(name);
   CPPUNIT_ASSERT(f.isFile());
   CPPUNIT_ASSERT(f.remove());