diff --git a/include/ntapi/nt_string.h b/include/ntapi/nt_string.h
index 10a413b..1a6a451 100644
--- a/include/ntapi/nt_string.h
+++ b/include/ntapi/nt_string.h
@@ -21,6 +21,17 @@ typedef int __cdecl ntapi_snprintf(
 	const char * format,
 	...);
 
+typedef int __cdecl ntapi_vsprintf(
+	char * buffer,
+	const char * format,
+	va_list ap);
+
+typedef int __cdecl ntapi_vsnprintf(
+	char * buffer,
+	size_t size,
+	const char * format,
+	va_list ap);
+
 
 typedef size_t __cdecl ntapi_strlen(const char * str);
 
diff --git a/include/ntapi/ntapi.h b/include/ntapi/ntapi.h
index 3d3d4de..b596f32 100644
--- a/include/ntapi/ntapi.h
+++ b/include/ntapi/ntapi.h
@@ -363,6 +363,8 @@ typedef struct _ntapi_vtbl {
 	ntapi_memset *					memset;
 	ntapi_sprintf *					sprintf;
 	ntapi_snprintf *				snprintf;
+	ntapi_vsprintf *				vsprintf;
+	ntapi_vsnprintf *				vsnprintf;
 	/* imported symbols: tail */
 
 	/* alternate implementation */
diff --git a/src/internal/ntapi_hash_table.h b/src/internal/ntapi_hash_table.h
index 1eacf88..2dad1ad 100644
--- a/src/internal/ntapi_hash_table.h
+++ b/src/internal/ntapi_hash_table.h
@@ -133,9 +133,11 @@
 	{0x78327b0d,	(173)},	/* ZwSetVolumeInformationFile */ \
 	{0x78a28538,	(80)},	/* ZwAdjustPrivilegesToken */ \
 	{0x7b9f9b64,	(182)},	/* ZwOpenKey */ \
+	{0x7c868d67,	(252)},	/* _vsnprintf */ \
 	{0x7ccd8968,	(138)},	/* ZwCompleteConnectPort */ \
 	{0x7dfb3677,	(169)},	/* ZwSetEaFile */ \
 	{0x7e21039a,	(87)},	/* ZwCreateTimer */ \
+	{0x7e92a7a6,	(251)},	/* vsprintf */ \
 	{0x7ec723c2,	(122)},	/* ZwQueryPerformanceCounter */ \
 	{0x7f99ab33,	(145)},	/* ZwReadRequestData */ \
 	{0x81b18dcd,	(21)},	/* ZwQueryVirtualMemory */ \
@@ -262,6 +264,6 @@
 	{0xf425639c,	(104)},	/* ZwOpenMutant */ \
 	{0xfde47817,	(94)},	/* ZwSetEvent */ \
 
-#define __NT_IMPORTED_SYMBOLS_ARRAY_SIZE	251
+#define __NT_IMPORTED_SYMBOLS_ARRAY_SIZE	253
 
 #endif