diff --git a/rtl/wasi/system.pp b/rtl/wasi/system.pp
index 1cf9feb200..a9b2800f04 100644
--- a/rtl/wasi/system.pp
+++ b/rtl/wasi/system.pp
@@ -364,7 +364,7 @@ Begin
   paramcount := argc - 1;
 End;
 
-function paramstr(l: longint) : string;
+function paramstr(l: longint) : shortstring;
 begin
   if argv=nil then
     setup_arguments;