diff --git a/RichString.c b/RichString.c
index 159d08ca0..7d0f82aef 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>
 
@@ -75,8 +76,8 @@ static size_t mbstowcs_nonfatal(wchar_t* restrict dest, const char* restrict src
    mbstate_t ps = { 0 };
    bool broken = false;
 
-   while (n > 0) {
-      size_t ret = mbrtowc(dest, src, n, &ps);
+   while (written < n) {
+      size_t ret = mbrtowc(dest, src, SIZE_MAX, &ps);
       if (ret == (size_t)-1 || ret == (size_t)-2) {
          if (!broken) {
             broken = true;
@@ -84,7 +85,6 @@ static size_t mbstowcs_nonfatal(wchar_t* restrict dest, const char* restrict src
             written++;
          }
          src++;
-         n--;
          continue;
       }
 
@@ -97,7 +97,6 @@ static size_t mbstowcs_nonfatal(wchar_t* restrict dest, const char* restrict src
       dest++;
       written++;
       src += ret;
-      n -= ret;
    }
 
    return written;