@@ -119,7 +119,7 @@ if debug_setfenv then
          return setfenv(n, env), nil
       end
       if type(fn) ~= 'function' then
-         fn =(getmetatable(fn) or {}).__call or fn
+         fn = fn.call or (getmetatable(fn) or {}).__call or fn
       end
       return debug_setfenv(fn, env)
    end
@@ -135,7 +135,7 @@ else
          end
          fn = debug_getinfo(n, 'f').func
       elseif type(fn) ~= 'function' then
-         fn =(getmetatable(fn) or {}).__call or fn
+         fn = fn.call or (getmetatable(fn) or {}).__call or fn
       end
 
       local up, name = 0
@@ -174,7 +174,7 @@ if debug_getfenv then
          -- No need to recurse because Lua doesn't support nested functors.
          -- __call can only (sensibly) be a function, so no need to adjust
          -- stack frame offset either.
-         fn =(getmetatable(fn) or {}).__call or fn
+         fn = fn.call or (getmetatable(fn) or {}).__call or fn
       end
 
       -- In Lua 5.1, only debug.getfenv works on C functions; but it
@@ -193,7 +193,7 @@ else
       if n then
          fn = debug_getinfo(n + 1, 'f').func
       elseif type(fn) ~= 'function' then
-         fn = (getmetatable(fn) or {}).__call or fn
+         fn = fn.call or (getmetatable(fn) or {}).__call or fn
       end
 
       local name, env
 
@@ -1051,6 +1051,17 @@ specify std.debug:
     - it understands functables:
         M.setfenv (ft, env)
         expect (f (ft)).to_be (env)
+    - it prefers a functable call field environment: |
+        expect (luaproc [[
+          local M = require "std.debug"
+          local env = {tostring = tostring}
+          local fn = function (x) return tostring (x) end
+          local ft = setmetatable ({call = fn}, {
+            __call = function (self, ...) return self.call (...) end,
+          })
+          M.setfenv (fn, env)
+          assert (M.getfenv (ft) == env)
+        ]]).to_succeed_with ""
 
   - describe setfenv:
     - before:
@@ -1063,6 +1074,18 @@ specify std.debug:
     - it understands functables:
         f (ft, env)
         expect (fn (5)).to_be '"5"'
+    - it sets a functable call field environment: |
+        expect (luaproc [[
+          local M = require "std.debug"
+          local env = {tostring = function (x) return '"' .. tostring (x) .. '"' end}
+          local fn = function (x) return tostring (x) end
+          local ft = setmetatable ({call = fn}, {
+            __call = function (self, ...) return self.call (...) end,
+          })
+          M.setfenv (ft, env)
+          assert (M.getfenv (fn) == env)
+          assert (ft (42) == '"42"')
+        ]]).to_succeed_with ""
 
 
 - describe say: