diff --git a/lld/wasm/Driver.cpp b/lld/wasm/Driver.cpp
--- a/lld/wasm/Driver.cpp
+++ b/lld/wasm/Driver.cpp
@@ -441,10 +441,8 @@
 
 static UndefinedGlobal *
 createUndefinedGlobal(StringRef name, llvm::wasm::WasmGlobalType *type) {
-  auto *sym =
-      cast<UndefinedGlobal>(symtab->addUndefinedGlobal(name, name,
-                                                       defaultModule, 0,
-                                                       nullptr, type));
+  auto *sym = cast<UndefinedGlobal>(symtab->addUndefinedGlobal(
+      name, name, defaultModule, WASM_SYMBOL_UNDEFINED, nullptr, type));
   config->allowUndefinedSymbols.insert(sym->getName());
   sym->isUsedInRegularObj = true;
   return sym;
@@ -582,7 +580,8 @@
 };
 
 static Symbol *addUndefined(StringRef name) {
-  return symtab->addUndefinedFunction(name, "", "", 0, nullptr, nullptr, false);
+  return symtab->addUndefinedFunction(name, "", "", WASM_SYMBOL_UNDEFINED,
+                                      nullptr, nullptr, false);
 }
 
 // Handles -wrap option.
diff --git a/lld/wasm/InputFiles.cpp b/lld/wasm/InputFiles.cpp
--- a/lld/wasm/InputFiles.cpp
+++ b/lld/wasm/InputFiles.cpp
@@ -421,7 +421,7 @@
 
 Symbol *ObjFile::createUndefined(const WasmSymbol &sym, bool isCalledDirectly) {
   StringRef name = sym.Info.Name;
-  uint32_t flags = sym.Info.Flags;
+  uint32_t flags = sym.Info.Flags | WASM_SYMBOL_UNDEFINED;
 
   switch (sym.Info.Kind) {
   case WASM_SYMBOL_TYPE_FUNCTION:
@@ -509,6 +509,7 @@
   bool excludedByComdat = c != -1 && !keptComdats[c];
 
   if (objSym.isUndefined() || excludedByComdat) {
+    flags |= WASM_SYMBOL_UNDEFINED;
     if (objSym.isExecutable())
       return symtab->addUndefinedFunction(name, name, defaultModule, flags, &f,
                                           nullptr, true);
diff --git a/lld/wasm/SymbolTable.cpp b/lld/wasm/SymbolTable.cpp
--- a/lld/wasm/SymbolTable.cpp
+++ b/lld/wasm/SymbolTable.cpp
@@ -401,6 +401,7 @@
   LLVM_DEBUG(dbgs() << "addUndefinedFunction: " << name << " ["
                     << (sig ? toString(*sig) : "none")
                     << "] IsCalledDirectly:" << isCalledDirectly << "\n");
+  assert(flags && WASM_SYMBOL_UNDEFINED);
 
   Symbol *s;
   bool wasInserted;
@@ -443,6 +444,7 @@
 Symbol *SymbolTable::addUndefinedData(StringRef name, uint32_t flags,
                                       InputFile *file) {
   LLVM_DEBUG(dbgs() << "addUndefinedData: " << name << "\n");
+  assert(flags && WASM_SYMBOL_UNDEFINED);
 
   Symbol *s;
   bool wasInserted;
@@ -464,6 +466,7 @@
                                         InputFile *file,
                                         const WasmGlobalType *type) {
   LLVM_DEBUG(dbgs() << "addUndefinedGlobal: " << name << "\n");
+  assert(flags && WASM_SYMBOL_UNDEFINED);
 
   Symbol *s;
   bool wasInserted;