diff --git a/RichString.c b/RichString.c
index 390beb073..a81d45aad 100644
--- a/RichString.c
+++ b/RichString.c
@@ -12,6 +12,7 @@ in the source distribution for its full text.
 #include <assert.h>
 #include <ctype.h>
 #include <limits.h> // IWYU pragma: keep
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -70,7 +71,7 @@ static size_t mbstowcs_nonfatal(wchar_t* restrict dest, const char* restrict src
    bool broken = false;
 
    while (n > 0) {
-      size_t ret = mbrtowc(dest, src, n, &ps);
+      size_t ret = mbrtowc(dest, src, SIZE_MAX, &ps);
       if (ret == (size_t)-1 || ret == (size_t)-2) {
          if (!broken) {
             broken = true;
@@ -91,7 +92,7 @@ static size_t mbstowcs_nonfatal(wchar_t* restrict dest, const char* restrict src
       dest++;
       written++;
       src += ret;
-      n -= ret;
+      n--;
    }
 
    return written;