diff --git a/src/builtin_fg.cpp b/src/builtin_fg.cpp
index 7733b34c1..e7cdbe05c 100644
--- a/src/builtin_fg.cpp
+++ b/src/builtin_fg.cpp
@@ -102,7 +102,7 @@ int builtin_fg(parser_t &parser, io_streams_t &streams, wchar_t **argv) {
     }
 
     const wcstring ft = tok_first(j->command());
-    if (!ft.empty()) env_set_one(L"_", ENV_EXPORT, ft);
+    if (!ft.empty()) env_set_one(L"fish_title", ENV_EXPORT, ft);
     reader_write_title(j->command());
 
     job_promote(j);
diff --git a/src/env.cpp b/src/env.cpp
index f80efdd6d..a1e4f15ef 100644
--- a/src/env.cpp
+++ b/src/env.cpp
@@ -322,7 +322,7 @@ bool string_set_contains(const T &set, const wchar_t *val) {
 
 /// Check if a variable may not be set using the set command.
 static bool is_read_only(const wchar_t *val) {
-    const string_set_t env_read_only = {L"PWD", L"SHLVL", L"_", L"history", L"status", L"version", L"pid", L"hostname"};
+    const string_set_t env_read_only = {L"PWD", L"SHLVL", L"history", L"status", L"version", L"pid", L"hostname", L"fish_title"};
     return string_set_contains(env_read_only, val);
 }
 
diff --git a/src/reader.cpp b/src/reader.cpp
index 8e8e185f6..904ee004a 100644
--- a/src/reader.cpp
+++ b/src/reader.cpp
@@ -1620,7 +1620,7 @@ static void reader_interactive_init() {
 
     invalidate_termsize();
 
-    env_set_one(L"_", ENV_GLOBAL, L"fish");
+    env_set_one(L"fish_title", ENV_GLOBAL, L"fish");
 }
 
 /// Destroy data for interactive use.
@@ -1897,7 +1897,7 @@ void reader_run_command(parser_t &parser, const wcstring &cmd) {
 
     wcstring ft = tok_first(cmd);
 
-    if (!ft.empty()) env_set_one(L"_", ENV_GLOBAL, ft);
+    if (!ft.empty()) env_set_one(L"fish_title", ENV_GLOBAL, ft);
 
     reader_write_title(cmd);
 
@@ -1913,7 +1913,7 @@ void reader_run_command(parser_t &parser, const wcstring &cmd) {
 
     term_steal();
 
-    env_set_one(L"_", ENV_GLOBAL, program_name);
+    env_set_one(L"fish_title", ENV_GLOBAL, program_name);
 
 #ifdef HAVE__PROC_SELF_STAT
     proc_update_jiffies();