diff --git a/src/common.cpp b/src/common.cpp
index 7154f0ecb..539cd2133 100644
--- a/src/common.cpp
+++ b/src/common.cpp
@@ -428,26 +428,6 @@ void append_format(wcstring &str, const wchar_t *format, ...) {
     va_end(va);
 }
 
-const wchar_t *wcsvarname(const wchar_t *str) {
-    while (*str) {
-        if ((!iswalnum(*str)) && (*str != L'_')) {
-            return str;
-        }
-        str++;
-    }
-    return NULL;
-}
-
-const wchar_t *wcsvarname(const wcstring &str) { return wcsvarname(str.c_str()); }
-
-const wchar_t *wcsfuncname(const wcstring &str) { return wcschr(str.c_str(), L'/'); }
-
-bool wcsvarchr(wchar_t chr) { return iswalnum(chr) || chr == L'_'; }
-
-int fish_wcswidth(const wchar_t *str) { return fish_wcswidth(str, wcslen(str)); }
-
-int fish_wcswidth(const wcstring &str) { return fish_wcswidth(str.c_str(), str.size()); }
-
 wchar_t *quote_end(const wchar_t *pos) {
     wchar_t c = *pos;
 
diff --git a/src/common.h b/src/common.h
index 4449f898f..50100af8b 100644
--- a/src/common.h
+++ b/src/common.h
@@ -617,27 +617,6 @@ wcstring vformat_string(const wchar_t *format, va_list va_orig);
 void append_format(wcstring &str, const wchar_t *format, ...);
 void append_formatv(wcstring &str, const wchar_t *format, va_list ap);
 
-/// Test if the given string is a valid variable name.
-///
-/// \return null if this is a valid name, and a pointer to the first invalid character otherwise.
-const wchar_t *wcsvarname(const wchar_t *str);
-const wchar_t *wcsvarname(const wcstring &str);
-
-/// Test if the given string is a valid function name.
-///
-/// \return null if this is a valid name, and a pointer to the first invalid character otherwise.
-const wchar_t *wcsfuncname(const wcstring &str);
-
-/// Test if the given string is valid in a variable name.
-///
-/// \return true if this is a valid name, false otherwise.
-bool wcsvarchr(wchar_t chr);
-
-/// Convenience variants on fish_wcwswidth().
-///
-/// See fallback.h for the normal definitions.
-int fish_wcswidth(const wchar_t *str);
-int fish_wcswidth(const wcstring &str);
 
 /// This functions returns the end of the quoted substring beginning at \c in. The type of quoting
 /// character is detemrined by examining \c in. Returns 0 on error.
diff --git a/src/wutil.cpp b/src/wutil.cpp
index c7b826fd4..5a08b6aca 100644
--- a/src/wutil.cpp
+++ b/src/wutil.cpp
@@ -1,4 +1,5 @@
 // Wide character equivalents of various standard unix functions.
+#define FISH_NO_ISW_WRAPPERS
 #include "config.h"
 
 #include <assert.h>
@@ -470,6 +471,84 @@ int wrename(const wcstring &old, const wcstring &newv) {
     return rename(old_narrow.c_str(), new_narrow.c_str());
 }
 
+/// Return one if the code point is in the range we reserve for internal use.
+int fish_is_reserved_codepoint(wint_t wc) {
+    if (RESERVED_CHAR_BASE <= wc && wc < RESERVED_CHAR_END) return 1;
+    if (EXPAND_RESERVED_BASE <= wc && wc < EXPAND_RESERVED_END) return 1;
+    if (WILDCARD_RESERVED_BASE <= wc && wc < WILDCARD_RESERVED_END) return 1;
+    return 0;
+}
+
+/// Return one if the code point is in a Unicode private use area.
+int fish_is_pua(wint_t wc) {
+    if (PUA1_START <= wc && wc < PUA1_END) return 1;
+    if (PUA2_START <= wc && wc < PUA2_END) return 1;
+    if (PUA3_START <= wc && wc < PUA3_END) return 1;
+    return 0;
+}
+
+/// We need this because there are too many implementations that don't return the proper answer for
+/// some code points. See issue #3050.
+int fish_iswalnum(wint_t wc) {
+    if (fish_is_reserved_codepoint(wc)) return 0;
+    if (fish_is_pua(wc)) return 0;
+    return iswalnum(wc);
+}
+
+/// We need this because there are too many implementations that don't return the proper answer for
+/// some code points. See issue #3050.
+int fish_iswalpha(wint_t wc) {
+    if (fish_is_reserved_codepoint(wc)) return 0;
+    if (fish_is_pua(wc)) return 0;
+    return iswalpha(wc);
+}
+
+/// We need this because there are too many implementations that don't return the proper answer for
+/// some code points. See issue #3050.
+int fish_iswgraph(wint_t wc) {
+    if (fish_is_reserved_codepoint(wc)) return 0;
+    if (fish_is_pua(wc)) return 1;
+    return iswgraph(wc);
+}
+
+/// Test if the given string is a valid variable name.
+///
+/// \return null if this is a valid name, and a pointer to the first invalid character otherwise.
+const wchar_t *wcsvarname(const wchar_t *str) {
+    while (*str) {
+        if ((!fish_iswalnum(*str)) && (*str != L'_')) {
+            return str;
+        }
+        str++;
+    }
+    return NULL;
+}
+
+/// Test if the given string is a valid variable name.
+///
+/// \return null if this is a valid name, and a pointer to the first invalid character otherwise.
+const wchar_t *wcsvarname(const wcstring &str) { return wcsvarname(str.c_str()); }
+
+/// Test if the given string is a valid function name.
+///
+/// \return null if this is a valid name, and a pointer to the first invalid character otherwise.
+const wchar_t *wcsfuncname(const wcstring &str) { return wcschr(str.c_str(), L'/'); }
+
+/// Test if the given string is valid in a variable name.
+///
+/// \return true if this is a valid name, false otherwise.
+bool wcsvarchr(wchar_t chr) { return fish_iswalnum(chr) || chr == L'_'; }
+
+/// Convenience variants on fish_wcwswidth().
+///
+/// See fallback.h for the normal definitions.
+int fish_wcswidth(const wchar_t *str) { return fish_wcswidth(str, wcslen(str)); }
+
+/// Convenience variants on fish_wcwswidth().
+///
+/// See fallback.h for the normal definitions.
+int fish_wcswidth(const wcstring &str) { return fish_wcswidth(str.c_str(), str.size()); }
+
 file_id_t file_id_t::file_id_from_stat(const struct stat *buf) {
     assert(buf != NULL);
 
diff --git a/src/wutil.h b/src/wutil.h
index d0f1a7944..304c3b23c 100644
--- a/src/wutil.h
+++ b/src/wutil.h
@@ -59,6 +59,31 @@ int wmkdir(const wcstring &dir, int mode);
 
 int wrename(const wcstring &oldName, const wcstring &newName);
 
+#define PUA1_START 0xE000
+#define PUA1_END 0xF900
+#define PUA2_START 0xF0000
+#define PUA2_END 0xFFFFE
+#define PUA3_START 0x100000
+#define PUA3_END 0x10FFFE
+
+// We need this because there are too many implementations that don't return the proper answer for
+// some code points. See issue #3050.
+#ifndef FISH_NO_ISW_WRAPPERS
+#define iswalnum fish_iswalnum
+#define iswalpha fish_iswalpha
+#define iswgraph fish_iswgraph
+#endif
+int fish_iswalnum(wint_t wc);
+int fish_iswalpha(wint_t wc);
+int fish_iswgraph(wint_t wc);
+
+const wchar_t *wcsvarname(const wchar_t *str);
+const wchar_t *wcsvarname(const wcstring &str);
+const wchar_t *wcsfuncname(const wcstring &str);
+bool wcsvarchr(wchar_t chr);
+int fish_wcswidth(const wchar_t *str);
+int fish_wcswidth(const wcstring &str);
+
 /// Class for representing a file's inode. We use this to detect and avoid symlink loops, among
 /// other things. While an inode / dev pair is sufficient to distinguish co-existing files, Linux
 /// seems to aggressively re-use inodes, so it cannot determine if a file has been deleted (ABA