diff --git a/linebuffer.c b/linebuffer.c
index df661f8..41dfa08 100644
--- a/linebuffer.c
+++ b/linebuffer.c
@@ -60,6 +60,7 @@ int linebuffer_put(struct linebuffer *buf, const char *src, unsigned int size)
 {
 	int len = MIN(buf->size - buf->pos, size);
 	memcpy(buf->data + buf->pos, src, len);
+	buf->pos += len;
 	return len;
 }
 
@@ -108,13 +109,9 @@ int linebuffer_writefd(struct linebuffer *buf, int fd)
 	return len;
 }
 
-int linebuffer_printf(struct linebuffer *buf, const char *fmt, ...)
+int linebuffer_vprintf(struct linebuffer *buf, const char *fmt, va_list az)
 {
-	va_list az;
-	va_start(az, fmt);
 	int len = vsnprintf(buf->data + buf->pos, buf->size - buf->pos, fmt, az);
-	va_end(az);
-
 	if (len < 0 || len >= (buf->size - buf->pos))
 		return -1;
 
@@ -122,6 +119,17 @@ int linebuffer_printf(struct linebuffer *buf, const char *fmt, ...)
 	return len;
 }
 
+int linebuffer_printf(struct linebuffer *buf, const char *fmt, ...)
+{
+	va_list az;
+
+	va_start(az, fmt);
+	int ret = linebuffer_vprintf(buf, fmt, az);
+	va_end(az);
+
+	return ret;
+}
+
 char * linebuffer_getline(struct linebuffer *buf, int *len)
 {
 	buf->newline = memchr(buf->data, '\n', buf->pos);
diff --git a/linebuffer.h b/linebuffer.h
index c021ad3..022db21 100644
--- a/linebuffer.h
+++ b/linebuffer.h
@@ -1,6 +1,8 @@
 #ifndef _LINEBUFFER_H_
 #define _LINEBUFFER_H_
 
+#include <stdarg.h>
+
 struct linebuffer {
 	unsigned int size;
 	unsigned int pos;
@@ -19,6 +21,7 @@ int linebuffer_parsefd(struct linebuffer *buf, int fd);
 int linebuffer_writefd(struct linebuffer *buf, int fd);
 
 int linebuffer_put(struct linebuffer *buf, const char *src, unsigned int size);
+int linebuffer_vprintf(struct linebuffer *buf, const char *fmt, va_list ap);
 int linebuffer_printf(struct linebuffer *buf, const char *fmt, ...);
 
 char * linebuffer_getline(struct linebuffer *buf, int *len);