diff --git a/doc/ca65.sgml b/doc/ca65.sgml
index fa3258562..03aa72097 100644
--- a/doc/ca65.sgml
+++ b/doc/ca65.sgml
@@ -1279,6 +1279,35 @@ Pseudo functions expect their arguments in parenthesis, and they have a result,
 either a string or an expression.
 
 
+<sect1><tt>.ADDRSIZE</tt><label id=".ADDRSIZE"><p>
+
+  The <tt/.ADDRSIZE/ function is used to return the interal address size 
+  associated with a symbol. This can be helpful in macros when knowing the address 
+  size of symbol can help with custom instructions.
+
+  Example:
+
+  <tscreen><verb>
+        .macro myLDA foo
+                .if .ADDRSIZE(foo) = 1
+                        ;do custom command based on zeropage addressing:
+                        .byte 0A5h, foo
+                .elseif .ADDRSIZE(foo) = 2
+                        ;do custom command based on absolute addressing:
+                        .byte 0ADh
+                        .word foo
+                .elseif .ADDRSIZE(foo) = 0
+                        ; no address size defined for this symbol:
+                        .out .sprintf("Error, address size unknown for symbol %s", .string(foo))
+                .endif
+        .endmacro
+  </verb></tscreen>
+
+  This command is new and must be enabled with the <tt/.FEATURE addrsize/ command.
+
+  See: <tt><ref id=".FEATURE" name=".FEATURE"></tt>
+
+
 <sect1><tt>.BANK</tt><label id=".BANK"><p>
 
   The <tt/.BANK/ function is used to support systems with banked memory. The
@@ -2596,6 +2625,12 @@ Here's a list of all control commands and a description, what they do:
 
   <descrip>
 
+  <tag><tt>addrsize</tt><label id="addrsize"></tag>
+
+    Enables the .ADDRSIZE pseudo function. This function is experimental and not enabled by default.
+
+    See also: <tt><ref id=".ADDRSIZE" name=".ADDRSIZE"></tt>
+
   <tag><tt>at_in_identifiers</tt><label id="at_in_identifiers"></tag>
 
     Accept the at character (`@') as a valid character in identifiers. The
diff --git a/src/ca65/expr.c b/src/ca65/expr.c
index e4d6f7363..8b87d0860 100644
--- a/src/ca65/expr.c
+++ b/src/ca65/expr.c
@@ -629,6 +629,85 @@ static ExprNode* FuncReferenced (void)
 
 
 
+static ExprNode* FuncAddrSize (void)
+/* Handle the .ADDRSIZE function */
+{
+    StrBuf    ScopeName = STATIC_STRBUF_INITIALIZER;
+    StrBuf    Name = STATIC_STRBUF_INITIALIZER;
+    SymEntry* Sym;
+    int       AddrSize;
+    int       NoScope;
+
+
+    /* Assume we don't know the size */
+    AddrSize = 0;
+
+    /* Check for a cheap local which needs special handling */
+    if (CurTok.Tok == TOK_LOCAL_IDENT) {
+
+        /* Cheap local symbol */
+        Sym = SymFindLocal (SymLast, &CurTok.SVal, SYM_FIND_EXISTING);
+        if (Sym == 0) {
+            Error ("Unknown symbol or scope: `%m%p'", &CurTok.SVal);
+        } else {
+            AddrSize = Sym->AddrSize;
+        }
+
+        /* Remember and skip SVal, terminate ScopeName so it is empty */
+        SB_Copy (&Name, &CurTok.SVal);
+        NextTok ();
+        SB_Terminate (&ScopeName);
+
+    } else {
+
+        /* Parse the scope and the name */
+        SymTable* ParentScope = ParseScopedIdent (&Name, &ScopeName);
+
+        /* Check if the parent scope is valid */
+        if (ParentScope == 0) {
+            /* No such scope */
+            SB_Done (&ScopeName);
+            SB_Done (&Name);
+            return GenLiteral0 ();
+        }
+
+        /* If ScopeName is empty, no explicit scope was specified. We have to
+        ** search upper scope levels in this case.
+        */
+        NoScope = SB_IsEmpty (&ScopeName);
+
+        /* If we did find a scope with the name, read the symbol defining the
+        ** size, otherwise search for a symbol entry with the name and scope.
+        */
+        if (NoScope) {
+            Sym = SymFindAny (ParentScope, &Name);
+        } else {
+            Sym = SymFind (ParentScope, &Name, SYM_FIND_EXISTING);
+        }
+        /* If we found the symbol retrieve the size, otherwise complain */
+        if (Sym) {
+            AddrSize = Sym->AddrSize;
+        } else {
+            Error ("Unknown symbol or scope: `%m%p%m%p'", &ScopeName, &Name);
+        }
+
+    }
+
+    if (AddrSize == 0) {
+        Warning (1, "Unknown address size: `%m%p%m%p'", &ScopeName, &Name);
+    }
+
+    /* Free the string buffers */
+    SB_Done (&ScopeName);
+    SB_Done (&Name);
+
+    /* Return the size. */
+
+    return GenLiteralExpr (AddrSize);
+}
+
+
+
 static ExprNode* FuncSizeOf (void)
 /* Handle the .SIZEOF function */
 {
@@ -965,6 +1044,10 @@ static ExprNode* Factor (void)
             N = Function (FuncBankByte);
             break;
 
+        case TOK_ADDRSIZE:
+            N = Function (FuncAddrSize);
+            break;
+
         case TOK_BLANK:
             N = Function (FuncBlank);
             break;
diff --git a/src/ca65/feature.c b/src/ca65/feature.c
index c398d2b37..3462d5501 100644
--- a/src/ca65/feature.c
+++ b/src/ca65/feature.c
@@ -63,6 +63,7 @@ static const char* FeatureKeys[FEAT_COUNT] = {
     "c_comments",
     "force_range",
     "underline_in_numbers",
+    "addrsize",
 };
 
 
@@ -119,6 +120,7 @@ feature_t SetFeature (const StrBuf* Key)
         case FEAT_C_COMMENTS:                 CComments         = 1;    break;
         case FEAT_FORCE_RANGE:                ForceRange        = 1;    break;
         case FEAT_UNDERLINE_IN_NUMBERS:       UnderlineInNumbers= 1;    break;
+        case FEAT_ADDRSIZE:                   AddrSize          = 1;    break;
         default:                         /* Keep gcc silent */          break;
     }
 
diff --git a/src/ca65/feature.h b/src/ca65/feature.h
index 9682ad9b9..3a520a54a 100644
--- a/src/ca65/feature.h
+++ b/src/ca65/feature.h
@@ -65,6 +65,7 @@ typedef enum {
     FEAT_C_COMMENTS,
     FEAT_FORCE_RANGE,
     FEAT_UNDERLINE_IN_NUMBERS,
+    FEAT_ADDRSIZE,
 
     /* Special value: Number of features available */
     FEAT_COUNT
diff --git a/src/ca65/global.c b/src/ca65/global.c
index b3d6d6c6e..77ed66e7f 100644
--- a/src/ca65/global.c
+++ b/src/ca65/global.c
@@ -82,3 +82,4 @@ unsigned char OrgPerSeg          = 0;   /* Make .org local to current seg */
 unsigned char CComments          = 0;   /* Allow C like comments */
 unsigned char ForceRange         = 0;   /* Force values into expected range */
 unsigned char UnderlineInNumbers = 0;   /* Allow underlines in numbers */
+unsigned char AddrSize           = 0;   /* Allow .ADDRSIZE function */
diff --git a/src/ca65/global.h b/src/ca65/global.h
index 378a776e6..fb254f835 100644
--- a/src/ca65/global.h
+++ b/src/ca65/global.h
@@ -84,6 +84,8 @@ extern unsigned char    OrgPerSeg;          /* Make .org local to current seg */
 extern unsigned char    CComments;          /* Allow C like comments */
 extern unsigned char    ForceRange;         /* Force values into expected range */
 extern unsigned char    UnderlineInNumbers; /* Allow underlines in numbers */
+extern unsigned char    AddrSize;           /* Allow .ADDRSIZE function */
+
 
 
 
diff --git a/src/ca65/pseudo.c b/src/ca65/pseudo.c
index 0b066c7bd..2e8a473a5 100644
--- a/src/ca65/pseudo.c
+++ b/src/ca65/pseudo.c
@@ -1964,6 +1964,7 @@ static CtrlDesc CtrlCmdTab [] = {
     { ccNone,           DoA16           },
     { ccNone,           DoA8            },
     { ccNone,           DoAddr          },      /* .ADDR */
+    { ccNone,           DoUnexpected    },      /* .ADDRSIZE */
     { ccNone,           DoAlign         },
     { ccNone,           DoASCIIZ        },
     { ccNone,           DoAssert        },
diff --git a/src/ca65/scanner.c b/src/ca65/scanner.c
index 890e1c7a3..db747cf70 100644
--- a/src/ca65/scanner.c
+++ b/src/ca65/scanner.c
@@ -135,6 +135,7 @@ struct DotKeyword {
     { ".A16",           TOK_A16         },
     { ".A8",            TOK_A8          },
     { ".ADDR",          TOK_ADDR        },
+    { ".ADDRSIZE",      TOK_ADDRSIZE    },
     { ".ALIGN",         TOK_ALIGN       },
     { ".AND",           TOK_BOOLAND     },
     { ".ASCIIZ",        TOK_ASCIIZ      },
@@ -723,7 +724,24 @@ static token_t FindDotKeyword (void)
     R = bsearch (&K, DotKeywords, sizeof (DotKeywords) / sizeof (DotKeywords [0]),
                  sizeof (DotKeywords [0]), CmpDotKeyword);
     if (R != 0) {
+
+        /* By default, disable any somewhat experiemental DotKeyword. */
+
+        switch (R->Tok) {
+
+            case TOK_ADDRSIZE:
+                /* Disallow .ADDRSIZE function by default */
+                if (AddrSize == 0) {
+                    return TOK_NONE;
+                }
+                break;
+
+            default:
+                break;
+        }
+
         return R->Tok;
+
     } else {
         return TOK_NONE;
     }
diff --git a/src/ca65/token.h b/src/ca65/token.h
index 803b12785..7aaba34c3 100644
--- a/src/ca65/token.h
+++ b/src/ca65/token.h
@@ -123,6 +123,7 @@ typedef enum token_t {
     TOK_A16             = TOK_FIRSTPSEUDO,
     TOK_A8,
     TOK_ADDR,
+    TOK_ADDRSIZE,
     TOK_ALIGN,
     TOK_ASCIIZ,
     TOK_ASSERT,