diff --git a/lib/Target/PowerPC/PPCAsmPrinter.cpp b/lib/Target/PowerPC/PPCAsmPrinter.cpp
index cc8c1f3e420..48eddb9527a 100644
--- a/lib/Target/PowerPC/PPCAsmPrinter.cpp
+++ b/lib/Target/PowerPC/PPCAsmPrinter.cpp
@@ -471,6 +471,7 @@ bool DarwinAsmPrinter::doFinalization(Module &M) {
           (I->hasInternalLinkage() || I->hasWeakLinkage() || 
            I->hasLinkOnceLinkage())) {
         SwitchSection(O, CurSection, ".data");
+        if (Size == 0) Size = 1;   // .comm Foo, 0 is undefined, avoid it.
         if (I->hasInternalLinkage())
           O << ".lcomm " << name << "," << Size << "," << Align;
         else