diff --git a/tools/bugpoint/ExtractFunction.cpp b/tools/bugpoint/ExtractFunction.cpp
index c3c7799e560..906826e0e5b 100644
--- a/tools/bugpoint/ExtractFunction.cpp
+++ b/tools/bugpoint/ExtractFunction.cpp
@@ -335,6 +335,9 @@ Module *BugDriver::ExtractMappedBlocksFromModule(const
   for (std::vector<BasicBlock*>::const_iterator I = BBs.begin(), E = BBs.end();
        I != E; ++I) {
     BasicBlock *BB = *I;
+    // If the BB doesn't have a name, give it one so we have something to key
+    // off of.
+    if (!BB->hasName()) BB->setName("tmpbb");
     BlocksToNotExtractFile << BB->getParent()->getName() << " "
                            << BB->getName() << "\n";
   }