diff --git a/src/macroexpand.scm b/src/macroexpand.scm
index b7b3e78c994ce..ea341c928eb18 100644
--- a/src/macroexpand.scm
+++ b/src/macroexpand.scm
@@ -59,9 +59,12 @@
    ;; function definition
    (pattern-lambda (function (-$ (call name . argl) (|::| (call name . argl) _t)) body)
                    (cons 'varlist (safe-llist-positional-args (fix-arglist argl))))
-   (pattern-lambda (function (where (-$ (call name . argl) (|::| (call name . argl) _t)) . wheres) body)
-                   (cons 'varlist (append (safe-llist-positional-args (fix-arglist argl))
-                                          (typevar-names wheres))))
+   (pattern-lambda (function (where callspec . wheres) body)
+                   (let ((others (pattern-expand1 vars-introduced-by-patterns `(function ,callspec ,body))))
+                     (cons 'varlist (append (if (and (pair? others) (eq? (car others) 'varlist))
+                                                (cdr others)
+                                                '())
+                                            (typevar-names wheres)))))
 
    (pattern-lambda (function (tuple . args) body)
                    `(-> (tuple ,@args) ,body))
@@ -71,7 +74,7 @@
                    `(function (call (curly ,name . ,sparams) . ,argl) ,body))
    (pattern-lambda (= (-$ (call name . argl) (|::| (call name . argl) _t)) body)
                    `(function (call ,name ,@argl) ,body))
-   (pattern-lambda (= (where (-$ (call name . argl) (|::| (call name . argl) _t)) . wheres) body)
+   (pattern-lambda (= (where callspec . wheres) body)
                    (cons 'function (cdr __)))
 
    ;; anonymous function
@@ -150,14 +153,14 @@
 
    (pattern-lambda (function (-$ (call name . argl) (|::| (call name . argl) _t)) body)
                    (cons 'varlist (safe-llist-keyword-args (fix-arglist argl))))
-   (pattern-lambda (function (where (-$ (call name . argl) (|::| (call name . argl) _t)) . wheres) body)
-                   (cons 'varlist (safe-llist-keyword-args (fix-arglist argl))))
+   (pattern-lambda (function (where callspec . wheres) body)
+                   `(function ,callspec ,body))
 
    (pattern-lambda (= (call (curly name . sparams) . argl) body)
                    `(function (call (curly ,name . ,sparams) . ,argl) ,body))
    (pattern-lambda (= (-$ (call name . argl) (|::| (call name . argl) _t)) body)
                    `(function (call ,name ,@argl) ,body))
-   (pattern-lambda (= (where (-$ (call name . argl) (|::| (call name . argl) _t)) . wheres) body)
+   (pattern-lambda (= (where callspec . wheres) body)
                    (cons 'function (cdr __)))
    ))
 
diff --git a/test/syntax.jl b/test/syntax.jl
index 7cdbc55178c67..8b81d16638b23 100644
--- a/test/syntax.jl
+++ b/test/syntax.jl
@@ -1489,3 +1489,15 @@ let val(::Type{Val{X}}) where {X} = X, f
     end
     @test val(first(methods(f())).sig.parameters[2])(21) == 42
 end
+
+# issue #27807
+module A27807
+macro m()
+    quote
+        function foo(x::T, y::S) where T<:Number where S<:Number
+            return one(T), zero(S)
+        end
+    end
+end
+end
+@test A27807.@m()(1,1.0) === (1, 0.0)