diff --git a/include/libbb.h b/include/libbb.h
index 152fb7e01..5cba27932 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -317,17 +317,11 @@ struct suffix_mult {
 };
 #include "xatonum.h"
 /* Specialized: */
-unsigned xatou_range(const char *numstr, unsigned lower, unsigned upper);
-unsigned xatou_sfx(const char *numstr, const struct suffix_mult *suffixes);
-unsigned xatou(const char *numstr);
-int xatoi_range(const char *numstr, int lower, int upper);
-int xatoi(const char *numstr);
 /* Using xatoi() instead of naive atoi() is not always convenient -
  * in many places people want *non-negative* values, but store them
  * in signed int. Therefore we need this one:
  * dies if input is not in [0, INT_MAX] range. Also will reject '-0' etc */
 int xatoi_u(const char *numstr);
-uint32_t xatou32(const char *numstr);
 /* Useful for reading port numbers */
 uint16_t xatou16(const char *numstr);
 
diff --git a/include/xatonum.h b/include/xatonum.h
index cdb5e7393..46e49b0eb 100644
--- a/include/xatonum.h
+++ b/include/xatonum.h
@@ -92,3 +92,15 @@ DEFINE_EQUIV_STR_CONV(int, i, l, u, ul)
 #else
 DECLARE_STR_CONV(int, i, u)
 #endif
+
+/* Specialized */
+
+int BUG_xatou32_unimplemented(void);
+extern inline uint32_t xatou32(const char *numstr)
+{
+	if (UINT_MAX == 0xffffffff)
+		return xatou(numstr);
+	if (ULONG_MAX == 0xffffffff)
+		return xatoul(numstr);
+	return BUG_xatou32_unimplemented();
+}
diff --git a/libbb/xatonum.c b/libbb/xatonum.c
index 910667c14..0d487dd9b 100644
--- a/libbb/xatonum.c
+++ b/libbb/xatonum.c
@@ -52,6 +52,15 @@
 #endif
 
 #if UINT_MAX != ULONG_MAX
+extern inline unsigned bb_strtoui(const char *str, char **end, int b)
+{
+	unsigned long v = strtoul(str, end, b);
+	if (v > UINT_MAX) {
+		errno = ERANGE;
+		return UINT_MAX;
+	}
+	return v;
+}
 #define type int
 #define xstrtou(rest) xstrtou##rest
 #define xstrto(rest) xstrtoi##rest
@@ -60,7 +69,8 @@
 #define XSTR_UTYPE_MAX UINT_MAX
 #define XSTR_TYPE_MAX INT_MAX
 #define XSTR_TYPE_MIN INT_MIN
-#define XSTR_STRTOU strtoul
+/* libc has no strtoui, so we need to create/use our own */
+#define XSTR_STRTOU bb_strtoui
 #include "xatonum_template.c"
 #undef type
 #undef xstrtou
@@ -77,7 +87,7 @@
 
 int xatoi_u(const char *numstr)
 {
-	return xatoul_range(numstr, 0, INT_MAX);
+	return xatou_range(numstr, 0, INT_MAX);
 }
 
 uint32_t xatou32(const char *numstr)
@@ -87,5 +97,5 @@ uint32_t xatou32(const char *numstr)
 
 uint16_t xatou16(const char *numstr)
 {
-	return xatoul_range(numstr, 0, 0xffff);
+	return xatou_range(numstr, 0, 0xffff);
 }