diff --git a/reactos/lib/rtl/unicode.c b/reactos/lib/rtl/unicode.c
index 9b29db30cf4..d14073cd8f8 100644
--- a/reactos/lib/rtl/unicode.c
+++ b/reactos/lib/rtl/unicode.c
@@ -625,7 +625,7 @@ RtlIntegerToUnicodeString(
    IN OUT PUNICODE_STRING String)
 {
     ANSI_STRING AnsiString;
-    CHAR Buffer[16];
+    CHAR Buffer[33];
     NTSTATUS Status;
 
     Status = RtlIntegerToChar(Value, Base, sizeof(Buffer), Buffer);
@@ -653,7 +653,7 @@ RtlInt64ToUnicodeString (
 {
     LARGE_INTEGER LargeInt;
     ANSI_STRING AnsiString;
-    CHAR Buffer[32];
+    CHAR Buffer[65];
     NTSTATUS Status;
 
     LargeInt.QuadPart = Value;