diff --git a/src/ca65/feature.c b/src/ca65/feature.c
index 8b915cfda..9f5ca5876 100644
--- a/src/ca65/feature.c
+++ b/src/ca65/feature.c
@@ -121,8 +121,6 @@ void SetFeature (feature_t Feature, unsigned char On)
         case FEAT_BRACKET_AS_INDIRECT:        BracketAsIndirect = On;    break;
         case FEAT_STRING_ESCAPES:             StringEscapes     = On;    break;
         case FEAT_LONG_JSR_JMP_RTS:           LongJsrJmpRts     = On;    break;
-        /* Accept, but ignore addrsize */
-        case FEAT_ADDRSIZE:                                              break;
         default:                                                         break;
     }
 }
diff --git a/src/ca65/pseudo.c b/src/ca65/pseudo.c
index 1877512d5..cf4d1f64b 100644
--- a/src/ca65/pseudo.c
+++ b/src/ca65/pseudo.c
@@ -1043,6 +1043,12 @@ static void DoFeature (void)
             ErrorSkip ("Invalid feature: '%m%p'", &CurTok.SVal);
             return;
         }
+
+        if (Feature == FEAT_ADDRSIZE) {
+            /* Warn for depreciated .feature addrsize */
+            Warning (1, "Depreciated feature: '.feature addrsize'. Pseudo function .addrsize is always available.");
+        }
+
         NextTok ();
 
         /* Optional +/- or ON/OFF */