diff --git a/compiler/options.pas b/compiler/options.pas
index 8d6c29b9e4..21932bc540 100644
--- a/compiler/options.pas
+++ b/compiler/options.pas
@@ -897,7 +897,7 @@ begin
                       initoptimizerswitches:=initoptimizerswitches+level3optimizerswitches;
                     'a' :
                       begin
-                        if not(UpdateAlignmentStr(Copy(Opt,j+1,255),ParaAlignment)) then
+                        if not(UpdateAlignmentStr(Copy(Opt,j+3,255),ParaAlignment)) then
                           IllegalPara(opt);
                         break;
                       end;