diff --git a/src/complete.cpp b/src/complete.cpp
index 1a62e964f..bda719620 100644
--- a/src/complete.cpp
+++ b/src/complete.cpp
@@ -903,7 +903,7 @@ bool completer_t::complete_param(const wcstring &cmd_orig, const wcstring &popt,
     bool head_exists = builtin_exists(cmd);
     // Only reload environment variables if builtin_exists returned false, as an optimization
     if (head_exists == false) {
-        head_exists = function_exists_no_autoload(cmd, vars);
+        head_exists = function_exists_no_autoload(cmd);
         // While it may seem like first testing `path_get_path` before resorting to an env lookup
         // may be faster, path_get_path can potentially do a lot of FS/IO access, so env.get() +
         // function_exists() should still be faster.
diff --git a/src/function.cpp b/src/function.cpp
index 0e220eee2..c54c76671 100644
--- a/src/function.cpp
+++ b/src/function.cpp
@@ -226,8 +226,7 @@ void function_load(const wcstring &cmd, parser_t &parser) {
     }
 }
 
-int function_exists_no_autoload(const wcstring &cmd, const environment_t &vars) {
-    (void)vars;
+int function_exists_no_autoload(const wcstring &cmd) {
     if (parser_keywords_is_reserved(cmd)) return 0;
     auto funcset = function_set.acquire();
 
diff --git a/src/function.h b/src/function.h
index dcfb14cb8..80cc39ace 100644
--- a/src/function.h
+++ b/src/function.h
@@ -77,7 +77,7 @@ int function_exists(const wcstring &name, parser_t &parser);
 void function_load(const wcstring &name, parser_t &parser);
 
 /// Returns true if the function with the name name exists, without triggering autoload.
-int function_exists_no_autoload(const wcstring &name, const environment_t &vars);
+int function_exists_no_autoload(const wcstring &name);
 
 /// Returns all function names.
 ///
diff --git a/src/highlight.cpp b/src/highlight.cpp
index 88fb88223..529745ea9 100644
--- a/src/highlight.cpp
+++ b/src/highlight.cpp
@@ -461,8 +461,7 @@ bool autosuggest_validate_from_history(const history_item_t &item,
     bool cmd_ok = false;
     if (path_get_path(parsed_command, NULL, vars)) {
         cmd_ok = true;
-    } else if (builtin_exists(parsed_command) ||
-               function_exists_no_autoload(parsed_command, vars)) {
+    } else if (builtin_exists(parsed_command) || function_exists_no_autoload(parsed_command)) {
         cmd_ok = true;
     }
 
@@ -1122,7 +1121,7 @@ static bool command_is_valid(const wcstring &cmd, enum parse_statement_decoratio
     if (!is_valid && builtin_ok) is_valid = builtin_exists(cmd);
 
     // Functions
-    if (!is_valid && function_ok) is_valid = function_exists_no_autoload(cmd, vars);
+    if (!is_valid && function_ok) is_valid = function_exists_no_autoload(cmd);
 
     // Abbreviations
     if (!is_valid && abbreviation_ok) is_valid = expand_abbreviation(cmd, vars).has_value();