diff --git a/reactos/dll/ntdll/def/ntdll.def b/reactos/dll/ntdll/def/ntdll.def
index 233d8f9dc32..b565636186d 100644
--- a/reactos/dll/ntdll/def/ntdll.def
+++ b/reactos/dll/ntdll/def/ntdll.def
@@ -1065,6 +1065,7 @@ strspn
 strstr
 strtol
 strtoul
+strtoull
 swprintf
 tan
 tolower
diff --git a/reactos/dll/win32/crtdll/crtdll.def b/reactos/dll/win32/crtdll/crtdll.def
index d463c84eddb..a9690a3ff60 100644
--- a/reactos/dll/win32/crtdll/crtdll.def
+++ b/reactos/dll/win32/crtdll/crtdll.def
@@ -523,6 +523,7 @@ strtod
 strtok
 strtol=NTDLL.strtol
 strtoul
+strtoull
 strxfrm
 swprintf=crt_swprintf
 swscanf
diff --git a/reactos/dll/win32/msvcrt/msvcrt.def b/reactos/dll/win32/msvcrt/msvcrt.def
index 8a53d6ef681..659ba94564b 100644
--- a/reactos/dll/win32/msvcrt/msvcrt.def
+++ b/reactos/dll/win32/msvcrt/msvcrt.def
@@ -797,6 +797,7 @@ strtod
 strtok
 strtol=NTDLL.strtol
 strtoul
+strtoull
 strxfrm
 swprintf=crt_swprintf
 swscanf
diff --git a/reactos/lib/sdk/libcntpr/libcntpr.rbuild b/reactos/lib/sdk/libcntpr/libcntpr.rbuild
index a03c9403d5a..b8f79ea2d0d 100644
--- a/reactos/lib/sdk/libcntpr/libcntpr.rbuild
+++ b/reactos/lib/sdk/libcntpr/libcntpr.rbuild
@@ -137,6 +137,7 @@
         <file>splitp.c</file>
         <file>strtol.c</file>
         <file>strtoul.c</file>
+        <file>strtoull.c</file>
         <file>wcstol.c</file>
         <file>wcstombs.c</file>
         <file>wcstoul.c</file>
diff --git a/reactos/lib/sdk/libcntpr/string/strtoul.c b/reactos/lib/sdk/libcntpr/string/strtoul.c
index 3ff15e66230..fcd735485e2 100644
--- a/reactos/lib/sdk/libcntpr/string/strtoul.c
+++ b/reactos/lib/sdk/libcntpr/string/strtoul.c
@@ -1,7 +1,10 @@
+#include <stdio.h>
 #include <string.h>
+#include <errno.h>
 #include <limits.h>
 #include <ctype.h>
 
+
 /*
  * Convert a string to an unsigned long integer.
  *
@@ -64,6 +67,7 @@ strtoul(const char *nptr, char **endptr, int base)
   if (any < 0)
   {
     acc = ULONG_MAX;
+
   }
   else if (neg)
     acc = -acc;