diff --git a/src/vim9compile.c b/src/vim9compile.c
index 94f30d4..bcbc57d 100644
--- a/src/vim9compile.c
+++ b/src/vim9compile.c
@@ -1592,6 +1592,7 @@
     garray_T	*stack = &cctx->ctx_type_stack;
     int		argoff;
     type_T	**argtypes = NULL;
+    type_T	*maptype = NULL;
 
     RETURN_OK_IF_SKIP(cctx);
     argoff = check_internal_func(func_idx, argcount);
@@ -1612,6 +1613,8 @@
 	argtypes = ((type_T **)stack->ga_data) + stack->ga_len - argcount;
 	if (internal_func_check_arg_types(argtypes, func_idx, argcount) == FAIL)
 	    return FAIL;
+	if (internal_func_is_map(func_idx))
+	    maptype = *argtypes;
     }
 
     if ((isn = generate_instr(cctx, ISN_BCALL)) == NULL)
@@ -1627,6 +1630,11 @@
 			  internal_func_ret_type(func_idx, argcount, argtypes);
     ++stack->ga_len;
 
+    if (maptype != NULL && maptype->tt_member != NULL
+					       && maptype->tt_member != &t_any)
+	// Check that map() didn't change the item types.
+	generate_TYPECHECK(cctx, maptype, -1);
+
     return OK;
 }