diff --git a/src/worker/builder.ts b/src/worker/builder.ts
index aa5f0585..27deaf92 100644
--- a/src/worker/builder.ts
+++ b/src/worker/builder.ts
@@ -591,7 +591,7 @@ function applySymbolConfigs(params, entries: string[]) {
 
 /**
  * Record a linker symbol. If the platform already passes `NAME=...` in
- * libargs, the entry is replaced in place -- appending instead would define the
+ * libargs (or `-g NAME=...` in extra_link_args), the entry is replaced in place -- appending instead would define the
  * symbol twice ("Redefinition of symbol", "Definition of public symbol ...").
  */
 function setLinkSymbol(params, symbols: PhaseLists, entry: string) {
@@ -606,6 +606,17 @@ function setLinkSymbol(params, symbols: PhaseLists, entry: string) {
       }
     }
   }
+  // sdldz80 platforms pass `-g NAME=...` pairs in extra_link_args
+  let xa = params.extra_link_args;
+  if (xa) {
+    for (let i = 1; i < xa.length; i++) {
+      if (xa[i - 1] === '-g' && xa[i].split('=')[0] === name) {
+        xa[i] = entry;
+        applySymbolConfigs(params, [entry]);
+        return;
+      }
+    }
+  }
   symbols.linker = mergeByName(symbols.linker, entry);
   applySymbolConfigs(params, [entry]);
 }
diff --git a/src/worker/tools/sdcc.ts b/src/worker/tools/sdcc.ts
index 70337fd5..69b05407 100644
--- a/src/worker/tools/sdcc.ts
+++ b/src/worker/tools/sdcc.ts
@@ -1,7 +1,7 @@
 import { Worker } from "node:worker_threads";
 import { defineArgs, extraArgsFor, linkSymbolArgs } from "../../common/toolmeta";
 import { CodeListingMap, WorkerError } from "../../common/workertypes";
-import { BuildStep, BuildStepResult, gatherFiles, staleFiles, populateFiles, putWorkFile, populateExtraFiles, anyTargetChanged, getWorkFileAsString } from "../builder";
+import { BuildStep, BuildStepResult, gatherFiles, staleFiles, populateFiles, putWorkFile, populateExtraFiles, anyTargetChanged, getWorkFileAsString, fixParamsWithDefines } from "../builder";
 import { parseListing, parseSourceLines, msvcErrorMatcher } from "../listingutils";
 import { EmscriptenModule, emglobal, execMain, loadNative, moduleInstFn, print_fn, setupFS, setupStdin } from "../wasmutils";
 import { preprocessMCPP } from "./mcpp";
@@ -266,6 +266,7 @@ export function compileSDCC(step: BuildStep): BuildStepResult {
     var params = step.params;
     var isGBZ80 = params.arch === 'gbz80';
     var outpath = step.prefix + ".asm";
+    fixParamsWithDefines(step.path, params); // //#symbol, //#flag, //#tooldef
     if (staleFiles(step, [outpath])) {
         var errors = [];
         loadNative('sdcc');
diff --git a/test/unit/testbuildparams.ts b/test/unit/testbuildparams.ts
index fc5e7075..aa741d5d 100644
--- a/test/unit/testbuildparams.ts
+++ b/test/unit/testbuildparams.ts
@@ -214,6 +214,14 @@ describe("explicit build directives (//#symbol, //#flag, //#tooldef)", function
     assert.deepStrictEqual(params.symbols.linker, []);
   });
 
+  it("#symbol ld replaces a matching -g entry in extra_link_args (sdldz80)", function () {
+    const params: any = { extra_link_args: ['-l', 'gb', '-g', 'GB_MAPPER=0x0', '-g', 'GB_RAM_SIZE=0x0'] };
+    applyDirectives("//#symbol ld GB_MAPPER=0x03\n//#symbol ld GB_RAM_SIZE=0x02\n", params);
+    assert.deepStrictEqual(params.extra_link_args, ['-l', 'gb', '-g', 'GB_MAPPER=0x03', '-g', 'GB_RAM_SIZE=0x02']);
+    // merged into extra_link_args, not queued again -> no duplicate -g on the link line
+    assert.deepStrictEqual(params.symbols.linker, []);
+  });
+
   it("#symbol ld queues a symbol that is not a platform libarg", function () {
     const params = nesParams();
     applyDirectives("//#symbol ld NEWSYM=0x10\n", params);