diff --git a/compat.c b/compat.c
index 1dfed886..44528641 100644
--- a/compat.c
+++ b/compat.c
@@ -338,13 +338,13 @@ WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
  *   sockets must be closed with closesocket() regardless.
  */
 
-int dumb_socketpair(int socks[2], int make_overlapped)
+OPENCONNECT_CMD_SOCKET dumb_socketpair(OPENCONNECT_CMD_SOCKET socks[2], int make_overlapped)
 {
     union {
        struct sockaddr_in inaddr;
        struct sockaddr addr;
     } a;
-    SOCKET listener;
+    OPENCONNECT_CMD_SOCKET listener;
     int e;
     socklen_t addrlen = sizeof(a.inaddr);
     DWORD flags = (make_overlapped ? WSA_FLAG_OVERLAPPED : 0);
diff --git a/library.c b/library.c
index 66db4587..efb7d063 100644
--- a/library.c
+++ b/library.c
@@ -435,21 +435,28 @@ void openconnect_set_cancel_fd(struct openconnect_info *vpninfo, int fd)
 	vpninfo->cmd_fd = fd;
 }
 
-int openconnect_setup_cmd_pipe(struct openconnect_info *vpninfo)
+#ifdef _WIN32
+# define CMD_PIPE_ERR INVALID_SOCKET
+#else
+# define CMD_PIPE_ERR -EIO
+#endif
+
+OPENCONNECT_CMD_SOCKET openconnect_setup_cmd_pipe(struct openconnect_info *vpninfo)
 {
-	int pipefd[2];
+	OPENCONNECT_CMD_SOCKET pipefd[2];
 
 #ifdef _WIN32
 	if (dumb_socketpair(pipefd, 0))
-		return -EIO;
+		return CMD_PIPE_ERR;
 #else
 	if (pipe(pipefd) < 0)
-		return -EIO;
+		return CMD_PIPE_ERR;
 #endif
+
 	if (set_sock_nonblock(pipefd[0]) || set_sock_nonblock(pipefd[1])) {
 		close(pipefd[0]);
 		close(pipefd[1]);
-		return -EIO;
+		return CMD_PIPE_ERR;
 	}
 	vpninfo->cmd_fd = pipefd[0];
 	vpninfo->cmd_fd_write = pipefd[1];
diff --git a/openconnect-internal.h b/openconnect-internal.h
index bf25338a..f25b5537 100644
--- a/openconnect-internal.h
+++ b/openconnect-internal.h
@@ -527,9 +527,11 @@ void openconnect__win32_sock_init();
 #undef inet_pton
 #define inet_pton openconnect__win32_inet_pton
 int openconnect__win32_inet_pton(int af, const char *src, void *dst);
-int dumb_socketpair(int socks[2], int make_overlapped);
+#define OPENCONNECT_CMD_SOCKET SOCKET
+OPENCONNECT_CMD_SOCKET dumb_socketpair(OPENCONNECT_CMD_SOCKET socks[2], int make_overlapped);
 #else
 #define closesocket close
+#define OPENCONNECT_CMD_SOCKET int
 #ifndef O_BINARY
 #define O_BINARY 0
 #endif
diff --git a/openconnect.h b/openconnect.h
index ea0e0094..6ec9abf5 100644
--- a/openconnect.h
+++ b/openconnect.h
@@ -390,7 +390,12 @@ void openconnect_set_cancel_fd(struct openconnect_info *vpninfo, int fd);
    to the library. This returns a file descriptor to the write side of
    the pipe. Both sides will be closed by openconnect_vpninfo_free().
    This replaces openconnect_set_cancel_fd(). */
-int openconnect_setup_cmd_pipe(struct openconnect_info *vpninfo);
+#ifdef _WIN32
+SOCKET
+#else
+int
+#endif
+openconnect_setup_cmd_pipe(struct openconnect_info *vpninfo);
 
 const char *openconnect_get_version(void);