diff --git a/llvm/tools/llvm-cov/TestingSupport.cpp b/llvm/tools/llvm-cov/TestingSupport.cpp
index f6c91f8..a662a15 100644
--- a/llvm/tools/llvm-cov/TestingSupport.cpp
+++ b/llvm/tools/llvm-cov/TestingSupport.cpp
@@ -88,7 +88,11 @@
   OS << "llvmcovmtestdata";
   encodeULEB128(ProfileNamesData.size(), OS);
   encodeULEB128(ProfileNamesAddress, OS);
-  OS << ProfileNamesData << CoverageMappingData;
+  OS << ProfileNamesData;
+  // Coverage mapping data is expected to have an alignment of 8.
+  for (unsigned Pad = OffsetToAlignment(OS.tell(), 8); Pad; --Pad)
+    OS.write(uint8_t(0));
+  OS << CoverageMappingData;
 
   return 0;
 }