diff --git a/src/evalfunc.c b/src/evalfunc.c
index e635116..ec74fde 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -2055,6 +2055,18 @@
 }
 
 /*
+ * Get the argument count for function "idx".
+ * "argcount" is the total argument count, "min_argcount" the non-optional
+ * argument count.
+ */
+    void
+internal_func_get_argcount(int idx, int *argcount, int *min_argcount)
+{
+    *argcount = global_functions[idx].f_max_argc;
+    *min_argcount = global_functions[idx].f_min_argc;
+}
+
+/*
  * Call the "f_retfunc" function to obtain the return type of function "idx".
  * "argtypes" is the list of argument types or NULL when there are no
  * arguments.
diff --git a/src/proto/evalfunc.pro b/src/proto/evalfunc.pro
index c1ac55f..3faff29 100644
--- a/src/proto/evalfunc.pro
+++ b/src/proto/evalfunc.pro
@@ -6,6 +6,7 @@
 int has_internal_func(char_u *name);
 char *internal_func_name(int idx);
 int internal_func_check_arg_types(type_T **types, int idx, int argcount, cctx_T *cctx);
+void internal_func_get_argcount(int idx, int *argcount, int *min_argcount);
 type_T *internal_func_ret_type(int idx, int argcount, type_T **argtypes);
 int internal_func_is_map(int idx);
 int check_internal_func(int idx, int argcount);
@@ -21,7 +22,6 @@
 int dynamic_feature(char_u *feature);
 void mzscheme_call_vim(char_u *name, typval_T *args, typval_T *rettv);
 void range_list_materialize(list_T *list);
-float_T vim_round(float_T f);
 long do_searchpair(char_u *spat, char_u *mpat, char_u *epat, int dir, typval_T *skip, int flags, pos_T *match_pos, linenr_T lnum_stop, long time_limit);
 void f_string(typval_T *argvars, typval_T *rettv);
 /* vim: set ft=c : */
diff --git a/src/testdir/test_vim9_assign.vim b/src/testdir/test_vim9_assign.vim
index 86f890e..92ffa00 100644
--- a/src/testdir/test_vim9_assign.vim
+++ b/src/testdir/test_vim9_assign.vim
@@ -650,6 +650,15 @@
     d.dd[0] = 0
   END
   CheckDefExecFailure(lines, 'E1147:', 2)
+
+  lines =<< trim END
+      def OneArg(x: bool)
+      enddef
+      def TwoArgs(x: bool, y: bool)
+      enddef
+      var fl: list<func(bool, bool, bool)> = [OneArg, TwoArgs]
+  END
+  CheckDefExecAndScriptFailure(lines, 'E1012:', 5)
 enddef
 
 def Test_assignment_list_any_index()
diff --git a/src/testdir/test_vim9_expr.vim b/src/testdir/test_vim9_expr.vim
index 22c68f4..1e99e95 100644
--- a/src/testdir/test_vim9_expr.vim
+++ b/src/testdir/test_vim9_expr.vim
@@ -57,7 +57,7 @@
       assert_equal(function('len'), Res)
 
       var RetOne: func(string): number = function('len')
-      var RetTwo: func(string): number = function('winnr')
+      var RetTwo: func(string): number = function('charcol')
       var RetThat: func = g:atrue ? RetOne : RetTwo
       assert_equal(function('len'), RetThat)
 
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index f4142ee..89cdee7 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -1030,7 +1030,7 @@
 
   lines =<< trim END
       vim9script
-      def g:TestFunc(f: func())
+      def g:TestFunc(f: func)
       enddef
       legacy call g:TestFunc({-> 0})
       delfunc g:TestFunc
diff --git a/src/version.c b/src/version.c
index 062e856..298fd87 100644
--- a/src/version.c
+++ b/src/version.c
@@ -756,6 +756,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3100,
+/**/
     3099,
 /**/
     3098,
diff --git a/src/vim9type.c b/src/vim9type.c
index 91dc3fe..c92e063 100644
--- a/src/vim9type.c
+++ b/src/vim9type.c
@@ -260,6 +260,7 @@
     type_T  *type;
     type_T  *member_type = &t_any;
     int	    argcount = 0;
+    int	    min_argcount = 0;
 
     if (tv->v_type == VAR_NUMBER)
 	return &t_number;
@@ -337,8 +338,7 @@
 
 	    if (idx >= 0)
 	    {
-		// TODO: get actual arg count and types
-		argcount = -1;
+		internal_func_get_argcount(idx, &argcount, &min_argcount);
 		member_type = internal_func_ret_type(idx, 0, NULL);
 	    }
 	    else
@@ -364,6 +364,7 @@
 	return NULL;
     type->tt_type = tv->v_type;
     type->tt_argcount = argcount;
+    type->tt_min_argcount = min_argcount;
     type->tt_member = member_type;
 
     return type;
@@ -525,9 +526,9 @@
 		ret = check_type(expected->tt_member, actual->tt_member,
 								 FALSE, where);
 	    if (ret == OK && expected->tt_argcount != -1
-		    && actual->tt_argcount != -1
-		    && (actual->tt_argcount < expected->tt_min_argcount
-			|| actual->tt_argcount > expected->tt_argcount))
+		    && (actual->tt_argcount == -1
+			|| (actual->tt_argcount < expected->tt_min_argcount
+			    || actual->tt_argcount > expected->tt_argcount)))
 		ret = FAIL;
 	    if (ret == OK && expected->tt_args != NULL
 						    && actual->tt_args != NULL)
@@ -1032,7 +1033,10 @@
 		}
 	    }
 	    else
+		// Use -1 for "tt_argcount" to indicate an unknown number of
+		// arguments.
 		*dest = alloc_func_type(common, -1, type_gap);
+
 	    // Use the minimum of min_argcount.
 	    (*dest)->tt_min_argcount =
 			type1->tt_min_argcount < type2->tt_min_argcount