diff --git a/llvm/tools/llvm-cov/SourceCoverageView.cpp b/llvm/tools/llvm-cov/SourceCoverageView.cpp
index f9ce946..4170fb4 100644
--- a/llvm/tools/llvm-cov/SourceCoverageView.cpp
+++ b/llvm/tools/llvm-cov/SourceCoverageView.cpp
@@ -102,6 +102,7 @@
     return llvm::make_unique<SourceCoverageViewText>(SourceName, File, Options,
                                                      std::move(CoverageInfo));
   }
+  llvm_unreachable("Unknown coverage output format!");
 }
 
 void SourceCoverageView::print(raw_ostream &OS, bool WholeFile,