diff --git a/src/common.cpp b/src/common.cpp
index ccd8d803d..38313c6c2 100644
--- a/src/common.cpp
+++ b/src/common.cpp
@@ -1219,6 +1219,8 @@ maybe_t<size_t> read_unquoted_escape(const wchar_t *input, wcstring *result, boo
             for (size_t i = 0; i < chars; i++) {
                 long d = convert_digit(input[in_pos], base);
                 if (d < 0) {
+                    // If we have no digit, this is a tokenizer error.
+                    if (i == 0) errored = true;
                     break;
                 }
 
@@ -1226,7 +1228,7 @@ maybe_t<size_t> read_unquoted_escape(const wchar_t *input, wcstring *result, boo
                 in_pos++;
             }
 
-            if (res <= max_val) {
+            if (!errored && res <= max_val) {
                 result_char_or_none =
                     static_cast<wchar_t>((byte_literal ? ENCODE_DIRECT_BASE : 0) + res);
             } else {
diff --git a/tests/checks/basic.fish b/tests/checks/basic.fish
index 3befee0ed..cfade8f88 100644
--- a/tests/checks/basic.fish
+++ b/tests/checks/basic.fish
@@ -558,3 +558,13 @@ end
 # CHECKERR: for PWD in foo bar
 # CHECKERR: ^
 # XXX FIXME carat should point at PWD
+
+$fish -c 'echo \xtest'
+# CHECKERR: fish: Invalid token '\xtest'
+# CHECKERR: echo \xtest
+# CHECKERR: ^
+
+$fish -c 'echo \utest'
+# CHECKERR: fish: Invalid token '\utest'
+# CHECKERR: echo \utest
+# CHECKERR: ^