Index: test/wasm/undefined.ll
===================================================================
--- test/wasm/undefined.ll
+++ test/wasm/undefined.ll
@@ -2,25 +2,44 @@
 ; RUN: wasm-ld --check-signatures --allow-undefined -o %t.wasm %t.o
 
 ; Fails due to undefined 'foo' and also 'baz'
-; RUN: not wasm-ld --check-signatures --undefined=baz -o %t.wasm %t.o 2>&1 | FileCheck %s
-; CHECK: error: {{.*}}.o: undefined symbol: foo
-; CHECK: error: undefined symbol: baz
+; RUN: not wasm-ld --check-signatures --undefined=baz -o %t.wasm %t.o 2>&1 | FileCheck %s -check-prefix=CHECK-ERROR
+; CHECK-ERROR: error: {{.*}}.o: undefined symbol: foo
+; CHECK-ERROR: error: {{.*}}.o: undefined symbol: bar
+; CHECK-ERROR: error: undefined symbol: baz
 
 ; Succeeds if we pass a file containing 'foo' as --allow-undefined-file.
 ; RUN: echo 'foo' > %t.txt
+; RUN: echo 'bar' >> %t.txt
 ; RUN: wasm-ld --check-signatures --allow-undefined-file=%t.txt -o %t.wasm %t.o
+; RUN: obj2yaml %t.wasm | FileCheck %s
 
 ; Succeeds even if a missing symbol is added via --export
 ; RUN: wasm-ld --check-signatures --allow-undefined --export=xxx -o %t.wasm %t.o
 
 target triple = "wasm32-unknown-unknown-wasm"
 
-; Takes the address of the external foo() resulting in undefined external
-@bar = hidden local_unnamed_addr global i8* bitcast (i32 ()* @foo to i8*), align 4
+; Takes the address of the external function foo()
+@addr_func = local_unnamed_addr global i8* bitcast (i32 ()* @foo to i8*), align 4
+
+; Take the address of the external_data
+@addr_data = local_unnamed_addr global i32* @bar, align 4
 
 declare i32 @foo() #0
+@bar = external global i32
 
-define hidden void @_start() local_unnamed_addr #0 {
+define void @_start() local_unnamed_addr #0 {
 entry:
     ret void
 }
+
+; CHECK:        - Type:            IMPORT
+; CHECK-NEXT:     Imports:         
+; CHECK-NEXT:       - Module:          env
+; CHECK-NEXT:         Field:           foo
+; CHECK-NEXT:         Kind:            FUNCTION
+; CHECK-NEXT:         SigIndex:        0
+; CHECK-NEXT:       - Module:          env
+; CHECK-NEXT:         Field:           bar
+; CHECK-NEXT:         Kind:            GLOBAL
+; CHECK-NEXT:         GlobalType:      I32
+; CHECK-NEXT:         GlobalMutable:   false
Index: wasm/Symbols.cpp
===================================================================
--- wasm/Symbols.cpp
+++ wasm/Symbols.cpp
@@ -91,7 +91,6 @@
 
 void Symbol::setOutputIndex(uint32_t Index) {
   DEBUG(dbgs() << "setOutputIndex " << Name << " -> " << Index << "\n");
-  assert(!isa<DataSymbol>(this));
   assert(OutputIndex == INVALID_INDEX);
   OutputIndex = Index;
 }
Index: wasm/Writer.cpp
===================================================================
--- wasm/Writer.cpp
+++ wasm/Writer.cpp
@@ -183,10 +183,13 @@
     if (auto *FunctionSym = dyn_cast<FunctionSymbol>(Sym)) {
       Import.Kind = WASM_EXTERNAL_FUNCTION;
       Import.SigIndex = lookupType(*FunctionSym->getFunctionType());
-    } else {
-      auto *GlobalSym = cast<GlobalSymbol>(Sym);
+    } else if (auto *GlobalSym = dyn_cast<GlobalSymbol>(Sym)) {
       Import.Kind = WASM_EXTERNAL_GLOBAL;
       Import.Global = *GlobalSym->getGlobalType();
+    } else {
+      assert(isa<DataSymbol>(Sym));
+      Import.Kind = WASM_EXTERNAL_GLOBAL;
+      Import.Global = {WASM_TYPE_I32, false};
     }
     writeImport(OS, Import);
   }
@@ -651,7 +654,9 @@
   for (Symbol *Sym : Symtab->getSymbols()) {
     if (!Sym->isUndefined())
       continue;
-    if (isa<DataSymbol>(Sym))
+    // For data symbols we don't use imports in the relocatable output, instead
+    // these are in the explict symbol table.
+    if (isa<DataSymbol>(Sym) && Config->Relocatable)
       continue;
     if (Sym->isWeak() && !Config->Relocatable)
       continue;