diff --git a/lib_generic/vsprintf.c b/lib_generic/vsprintf.c
index 2740f2e..e9f7113 100755
--- a/lib_generic/vsprintf.c
+++ b/lib_generic/vsprintf.c
@@ -202,7 +202,7 @@
 	int field_width;	/* width of output field */
 	int precision;		/* min. # of digits for integers; max
 				   number of chars for from string */
-	int qualifier;		/* 'h', 'l', or 'q' for integer fields */
+	int qualifier;		/* 'h', 'l', 'q' or 'z' for integer fields */
 
 	for (str=buf ; *fmt ; ++fmt) {
 		if (*fmt != '%') {
@@ -253,7 +253,7 @@
 
 		/* get the conversion qualifier */
 		qualifier = -1;
-		if (*fmt == 'h' || *fmt == 'l' || *fmt == 'q') {
+		if (*fmt == 'h' || *fmt == 'l' || *fmt == 'q' || *fmt == 'z') {
 			qualifier = *fmt;
 			++fmt;
 		}
@@ -337,6 +337,16 @@
 				--fmt;
 			continue;
 		}
+		if (qualifier == 'z') {
+			switch (sizeof(size_t)) {
+			case sizeof(unsigned long):
+				qualifier = 'l';
+				break;
+			case sizeof(unsigned long long):
+				qualifier = 'q';
+				break;
+			}
+		}
 #ifdef CFG_64BIT_VSPRINTF
 		if (qualifier == 'q')  /* "quad" for 64 bit variables */
 			num = va_arg(args, unsigned long long);