diff --git a/core/klibc.c b/core/klibc.c
index 257095c..e3566a5 100644
--- a/core/klibc.c
+++ b/core/klibc.c
@@ -425,7 +425,8 @@ int vsnprintf(char *str, size_t size, const char *format, va_list ap)
                                     case 'x': {
                                         char val[sizeof(long long int) * 2];
                                         unsigned int valIdx = 0;
-                                        long long int d     = va_arg(ap, long long int);
+                                        unsigned long long int d =
+                                            va_arg(ap, unsigned long long int);
                                         itoa(d, val, 16);
                                         if (str) {
                                             while (val[valIdx]) {
@@ -453,7 +454,7 @@ int vsnprintf(char *str, size_t size, const char *format, va_list ap)
                             case 'x': {
                                 char val[sizeof(int) * 2];
                                 unsigned int valIdx = 0;
-                                long int d               = va_arg(ap, long int);
+                                unsigned long int d = va_arg(ap, unsigned long int);
                                 itoa(d, val, 16);
                                 if (str) {
                                     while (val[valIdx]) {