diff --git a/src/eval.c b/src/eval.c
index 0d41f17..769816d 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -3359,7 +3359,7 @@
 	{
 	    type_T *actual = typval2type(rettv, get_copyID(), &type_list, TRUE);
 
-	    if (!equal_type(want_type, actual))
+	    if (!equal_type(want_type, actual, 0))
 	    {
 		if (want_type == &t_bool && actual != &t_bool
 					&& (actual->tt_flags & TTFLAG_BOOL_OK))
diff --git a/src/proto/vim9type.pro b/src/proto/vim9type.pro
index 559eb5c..6e8f486 100644
--- a/src/proto/vim9type.pro
+++ b/src/proto/vim9type.pro
@@ -20,7 +20,7 @@
 int check_argument_types(type_T *type, typval_T *argvars, int argcount, char_u *name);
 char_u *skip_type(char_u *start, int optional);
 type_T *parse_type(char_u **arg, garray_T *type_gap, int give_error);
-int equal_type(type_T *type1, type_T *type2);
+int equal_type(type_T *type1, type_T *type2, int flags);
 void common_type(type_T *type1, type_T *type2, type_T **dest, garray_T *type_gap);
 type_T *get_member_type_from_stack(type_T **stack_top, int count, int skip, garray_T *type_gap);
 char *vartype_name(vartype_T type);
diff --git a/src/testdir/test_vim9_script.vim b/src/testdir/test_vim9_script.vim
index d46299c..4b9e6f3 100644
--- a/src/testdir/test_vim9_script.vim
+++ b/src/testdir/test_vim9_script.vim
@@ -1626,6 +1626,9 @@
   var lines =<< trim END
     vim9script
     export var exported = 'thexport'
+
+    export def TheFunc(x = 0)
+    enddef
   END
   writefile(lines, 'XExportReload')
   lines =<< trim END
@@ -1638,6 +1641,9 @@
       return 'again'
     enddef
 
+    import TheFunc from './XExportReload'
+    TheFunc()
+
     if exists('s:loaded') | finish | endif
     var s:loaded = true
 
diff --git a/src/version.c b/src/version.c
index 9510569..33f4196 100644
--- a/src/version.c
+++ b/src/version.c
@@ -756,6 +756,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3249,
+/**/
     3248,
 /**/
     3247,
diff --git a/src/vim.h b/src/vim.h
index 30cf284..54d507e 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -2736,4 +2736,7 @@
 // Maximum number of characters that can be fuzzy matched
 #define MAX_FUZZY_MATCHES	256
 
+// flags for equal_type()
+#define ETYPE_ARG_UNKNOWN 1
+
 #endif // VIM__H
diff --git a/src/vim9execute.c b/src/vim9execute.c
index 5c59c5b..f453af7 100644
--- a/src/vim9execute.c
+++ b/src/vim9execute.c
@@ -1271,7 +1271,7 @@
 	return NULL;
     }
     sv = ((svar_T *)si->sn_var_vals.ga_data) + sref->sref_idx;
-    if (!equal_type(sv->sv_type, sref->sref_type))
+    if (!equal_type(sv->sv_type, sref->sref_type, 0))
     {
 	emsg(_(e_script_variable_type_changed));
 	return NULL;
diff --git a/src/vim9script.c b/src/vim9script.c
index 641b0dd..40f857f 100644
--- a/src/vim9script.c
+++ b/src/vim9script.c
@@ -623,9 +623,10 @@
 		    && (imported->imp_flags & IMP_FLAGS_RELOAD)
 		    && imported->imp_sid == sid
 		    && (idx >= 0
-			? (equal_type(imported->imp_type, type)
+			? (equal_type(imported->imp_type, type, 0)
 			    && imported->imp_var_vals_idx == idx)
-			: (equal_type(imported->imp_type, ufunc->uf_func_type)
+			: (equal_type(imported->imp_type, ufunc->uf_func_type,
+							     ETYPE_ARG_UNKNOWN)
 			    && STRCMP(imported->imp_funcname,
 							ufunc->uf_name) == 0)))
 	    {
diff --git a/src/vim9type.c b/src/vim9type.c
index ea50e89..f64089a 100644
--- a/src/vim9type.c
+++ b/src/vim9type.c
@@ -954,9 +954,11 @@
 
 /*
  * Check if "type1" and "type2" are exactly the same.
+ * "flags" can have ETYPE_ARG_UNKNOWN, which means that an unknown argument
+ * type in "type1" is accepted.
  */
     int
-equal_type(type_T *type1, type_T *type2)
+equal_type(type_T *type1, type_T *type2, int flags)
 {
     int i;
 
@@ -981,17 +983,19 @@
 	    break;  // not composite is always OK
 	case VAR_LIST:
 	case VAR_DICT:
-	    return equal_type(type1->tt_member, type2->tt_member);
+	    return equal_type(type1->tt_member, type2->tt_member, flags);
 	case VAR_FUNC:
 	case VAR_PARTIAL:
-	    if (!equal_type(type1->tt_member, type2->tt_member)
+	    if (!equal_type(type1->tt_member, type2->tt_member, flags)
 		    || type1->tt_argcount != type2->tt_argcount)
 		return FALSE;
 	    if (type1->tt_argcount < 0
 			   || type1->tt_args == NULL || type2->tt_args == NULL)
 		return TRUE;
 	    for (i = 0; i < type1->tt_argcount; ++i)
-		if (!equal_type(type1->tt_args[i], type2->tt_args[i]))
+		if ((flags & ETYPE_ARG_UNKNOWN) == 0
+			&& !equal_type(type1->tt_args[i], type2->tt_args[i],
+									flags))
 		    return FALSE;
 	    return TRUE;
     }
@@ -1005,7 +1009,7 @@
     void
 common_type(type_T *type1, type_T *type2, type_T **dest, garray_T *type_gap)
 {
-    if (equal_type(type1, type2))
+    if (equal_type(type1, type2, 0))
     {
 	*dest = type1;
 	return;