diff --git a/src/builtin.cpp b/src/builtin.cpp
index 7731a9488..ed9d86566 100644
--- a/src/builtin.cpp
+++ b/src/builtin.cpp
@@ -483,6 +483,12 @@ proc_status_t builtin_run(parser_t &parser, const wcstring_list_t &argv, io_stre
         return proc_status_t::empty();
     }
     if (code < 0) {
+        // If the code is below 0, constructing a proc_status_t
+        // would assert() out, which is a terrible failure mode
+        // So instead, what we do is we get a positive code,
+        // and we avoid 0.
+        code = abs((256 + code) % 256);
+        if (code == 0) code = 255;
         FLOGF(warning, "builtin %ls returned invalid exit code %d", cmdname.c_str(), code);
     }
     return proc_status_t::from_exit_code(code);
diff --git a/tests/checks/status-value.fish b/tests/checks/status-value.fish
index 1a296acd9..9c9452130 100644
--- a/tests/checks/status-value.fish
+++ b/tests/checks/status-value.fish
@@ -1,4 +1,4 @@
-# RUN: %fish %s
+# RUN: %fish -C 'set -g fish %fish' %s
 
 # Empty commands should be 123
 set empty_var
@@ -24,3 +24,24 @@ echo $status
 # CHECKERR: {{.*}} No matches for wildcard '*gibberishgibberishgibberish*'. {{.*}}
 # CHECKERR: echo *gibberishgibberishgibberish*
 # CHECKERR:      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~^
+
+$fish -c 'exit -5'
+# CHECKERR: warning: builtin exit returned invalid exit code 251
+echo $status
+# CHECK: 251
+
+$fish -c 'exit -1'
+# CHECKERR: warning: builtin exit returned invalid exit code 255
+echo $status
+# CHECK: 255
+
+# (we avoid 0, so this is turned into 255 again)
+$fish -c 'exit -256'
+# CHECKERR: warning: builtin exit returned invalid exit code 255
+echo $status
+# CHECK: 255
+
+$fish -c 'exit -512'
+# CHECKERR: warning: builtin exit returned invalid exit code 255
+echo $status
+# CHECK: 255