diff --git a/src/ca65/condasm.c b/src/ca65/condasm.c
index 6198f4017..a874aa1c6 100644
--- a/src/ca65/condasm.c
+++ b/src/ca65/condasm.c
@@ -32,6 +32,8 @@
 /*****************************************************************************/
 
 
+#include "addrsize.h"
+#include "scopedefs.h"
 
 /* ca65 */
 #include "error.h"
@@ -42,6 +44,7 @@
 #include "symbol.h"
 #include "symtab.h"
 #include "condasm.h"
+#include "pseudo.h"
 
 
 
@@ -193,7 +196,7 @@ static void FreeIf (void)
     int Done;
     do {
         IfDesc* ID = GetCurrentIf();
-        if (ID == 0) {
+        if (ID == 0 || strcmp(ID->Name, ".WEAKPROC") == 0) {
             Error (" Unexpected .ENDIF");
             Done = 1;
         } else {
@@ -205,6 +208,23 @@ static void FreeIf (void)
     } while (!Done);
 }
 
+static void CheckNoWeak (void)
+{
+    int Done = 0;
+
+    do {
+        IfDesc* ID = GetCurrentIf();
+        if (ID == 0) {
+            Done = 1;
+        } else {
+            if (strcmp(ID->Name, ".WEAKPROC") == 0) {
+                Error (".WEAKPROC nesting not allowed");
+                Done = 1;
+            }
+        }
+    } while (!Done);
+}
+
 
 
 /*****************************************************************************/
@@ -282,6 +302,27 @@ void DoConditionals (void)
                 CalcOverallIfCond ();
                 break;
 
+            case TOK_ENDWEAK:
+                D = GetCurrentIf();
+                if (D == 0 || strcmp(D->Name, ".WEAKPROC") != 0) {
+                    Error ("Unexpected .ENDWEAK");
+                } else {
+                    ReleaseFullLineInfo (&D->LineInfos);
+                    DoneCollection (&D->LineInfos);
+                    --IfCount;
+                }
+                if (CurrentScope->Type != SCOPE_SCOPE || CurrentScope->Label == 0) {
+                } else {
+                    SymLeaveLevel ();
+                }
+
+                NextTok ();
+                ExpectSep ();
+
+                /* Get the new overall condition */
+                CalcOverallIfCond ();
+                break;
+
             case TOK_IF:
                 D = AllocIf (".IF", 1);
                 NextTok ();
@@ -447,6 +488,23 @@ void DoConditionals (void)
                 CalcOverallIfCond ();
                 break;
 
+            case TOK_WEAKPROC:
+                CheckNoWeak();
+                D = AllocIf (".WEAKPROC", 1);
+                NextTok ();
+                if (IfCond) {
+                    SymEntry* Sym = ParseAnySymName (SYM_FIND_EXISTING);
+                    SetIfCond (D, Sym != 0 && SymIsRef (Sym));
+
+                    if (Sym != 0) {
+                        SymDef (Sym, GenCurrentPC (), ADDR_SIZE_DEFAULT, SF_LABEL);
+                        SymEnterLevel (&CurTok.SVal, SCOPE_SCOPE, ADDR_SIZE_DEFAULT, Sym);
+                    }
+                    ExpectSep ();
+                }
+                CalcOverallIfCond ();
+                break;
+
             default:
                 /* Skip tokens */
                 NextTok ();
@@ -468,6 +526,7 @@ int CheckConditionals (void)
         case TOK_ELSE:
         case TOK_ELSEIF:
         case TOK_ENDIF:
+        case TOK_ENDWEAK:
         case TOK_IF:
         case TOK_IFBLANK:
         case TOK_IFCONST:
diff --git a/src/ca65/pseudo.c b/src/ca65/pseudo.c
index 2ce1ae087..3a6d5db51 100644
--- a/src/ca65/pseudo.c
+++ b/src/ca65/pseudo.c
@@ -2103,6 +2103,7 @@ static CtrlDesc CtrlCmdTab [] = {
     { ccNone,           DoEndScope      },
     { ccNone,           DoUnexpected    },      /* .ENDSTRUCT */
     { ccNone,           DoUnexpected    },      /* .ENDUNION */
+    { ccKeepToken,      DoConditionals  },      /* .ENDWEAK */
     { ccNone,           DoEnum          },
     { ccNone,           DoError         },
     { ccNone,           DoExitMacro     },
@@ -2203,6 +2204,7 @@ static CtrlDesc CtrlCmdTab [] = {
     { ccNone,           DoUnion         },
     { ccNone,           DoUnexpected    },      /* .VERSION */
     { ccNone,           DoWarning       },
+    { ccKeepToken,      DoConditionals  },      /* .WEAKPROC */
     { ccNone,           DoWord          },
     { ccNone,           DoUnexpected    },      /* .XMATCH */
     { ccNone,           DoZeropage      },
diff --git a/src/ca65/scanner.c b/src/ca65/scanner.c
index 185100025..2ef33ed0f 100644
--- a/src/ca65/scanner.c
+++ b/src/ca65/scanner.c
@@ -187,6 +187,7 @@ struct DotKeyword {
     { ".ENDSCOPE",      TOK_ENDSCOPE            },
     { ".ENDSTRUCT",     TOK_ENDSTRUCT           },
     { ".ENDUNION",      TOK_ENDUNION            },
+    { ".ENDWEAK",       TOK_ENDWEAK             },
     { ".ENUM",          TOK_ENUM                },
     { ".ERROR",         TOK_ERROR               },
     { ".EXITMAC",       TOK_EXITMACRO           },
@@ -300,6 +301,7 @@ struct DotKeyword {
     { ".UNION",         TOK_UNION               },
     { ".VERSION",       TOK_VERSION             },
     { ".WARNING",       TOK_WARNING             },
+    { ".WEAKPROC",      TOK_WEAKPROC            },
     { ".WORD",          TOK_WORD                },
     { ".XMATCH",        TOK_XMATCH              },
     { ".XOR",           TOK_BOOLXOR             },
diff --git a/src/ca65/token.h b/src/ca65/token.h
index b8bbb6d6e..1583b3033 100644
--- a/src/ca65/token.h
+++ b/src/ca65/token.h
@@ -165,6 +165,7 @@ typedef enum token_t {
     TOK_ENDSCOPE,
     TOK_ENDSTRUCT,
     TOK_ENDUNION,
+    TOK_ENDWEAK,
     TOK_ENUM,
     TOK_ERROR,
     TOK_EXITMACRO,
@@ -265,6 +266,7 @@ typedef enum token_t {
     TOK_UNION,
     TOK_VERSION,
     TOK_WARNING,
+    TOK_WEAKPROC,
     TOK_WORD,
     TOK_XMATCH,
     TOK_ZEROPAGE,