diff --git a/src/coff/coff_obj_writer.c b/src/coff/coff_obj_writer.c
index 3770fb12..016b2364 100644
--- a/src/coff/coff_obj_writer.c
+++ b/src/coff/coff_obj_writer.c
@@ -103,7 +103,7 @@ coff_obj_writer_serialize(Arena *arena, COFF_ObjWriter *obj_writer)
         if (s->aux_symbols.node_count > 0) {
           COFF_ObjSymbolWeak *s_weak = (COFF_ObjSymbolWeak *)s->aux_symbols.first->string.str;
           COFF_SymbolWeakExt *d_weak = push_array(scratch.arena, COFF_SymbolWeakExt, 1);
-          d_weak->tag_index       = s_weak->tag->idx;
+          d_weak->tag_index       = s_weak->tag ? s_weak->tag->idx : max_U32;
           d_weak->characteristics = s_weak->characteristics;
 
           str8_list_push(scratch.arena, &symbol_table, str8_struct(d_weak));
@@ -415,6 +415,14 @@ coff_obj_writer_push_symbol_common(COFF_ObjWriter *obj_writer, String8 name, U32
   return s;
 }
 
+internal void
+coff_obj_writer_set_default_symbol(COFF_ObjSymbol *weak_symbol, COFF_ObjSymbol *default_symbol)
+{
+  AssertAlways(weak_symbol->storage_class == COFF_SymStorageClass_WeakExternal);
+  COFF_ObjSymbolWeak *w = (COFF_ObjSymbolWeak *)weak_symbol->aux_symbols.first->string.str;
+  w->tag = default_symbol;
+}
+
 internal COFF_ObjReloc*
 coff_obj_writer_section_push_reloc(COFF_ObjWriter *obj_writer, COFF_ObjSection *sect, U32 apply_off, COFF_ObjSymbol *symbol, COFF_RelocType type)
 {
diff --git a/src/coff/coff_obj_writer.h b/src/coff/coff_obj_writer.h
index 9068822a..5b5e0248 100644
--- a/src/coff/coff_obj_writer.h
+++ b/src/coff/coff_obj_writer.h
@@ -115,6 +115,8 @@ internal COFF_ObjSymbol * coff_obj_writer_push_symbol_undef_sect(COFF_ObjWriter
 internal COFF_ObjSymbol * coff_obj_writer_push_symbol_sect(COFF_ObjWriter *obj_writer, String8 name, COFF_ObjSection *sect);
 internal COFF_ObjSymbol * coff_obj_writer_push_symbol_common(COFF_ObjWriter *obj_writer, String8 name, U32 size);
 
+internal void coff_obj_writer_set_default_symbol(COFF_ObjSymbol *weak_symbol, COFF_ObjSymbol *default_symbol);
+
 internal COFF_ObjReloc * coff_obj_writer_section_push_reloc(COFF_ObjWriter *obj_writer, COFF_ObjSection *sect, U32 apply_off, COFF_ObjSymbol *symbol, COFF_RelocType reloc_type);
 internal COFF_ObjReloc * coff_obj_writer_section_push_reloc_addr(COFF_ObjWriter *obj_writer, COFF_ObjSection *sect, U32 apply_off, COFF_ObjSymbol *symbol);
 internal COFF_ObjReloc * coff_obj_writer_section_push_reloc_voff(COFF_ObjWriter *obj_writer, COFF_ObjSection *sect, U32 apply_off, COFF_ObjSymbol *symbol);