diff --git a/llvm/lib/MC/MCStreamer.cpp b/llvm/lib/MC/MCStreamer.cpp
index 254eb2c..2e36fe7 100644
--- a/llvm/lib/MC/MCStreamer.cpp
+++ b/llvm/lib/MC/MCStreamer.cpp
@@ -1055,6 +1055,10 @@
 void MCStreamer::EmitCOFFSymbolType(int Type) {
   llvm_unreachable("this directive only supported on COFF targets");
 }
+void MCStreamer::EmitXCOFFLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
+                                            unsigned ByteAlign) {
+  llvm_unreachable("this directive only supported on XCOFF targets");
+}
 void MCStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {}
 void MCStreamer::emitELFSymverDirective(StringRef AliasName,
                                         const MCSymbol *Aliasee) {}