diff --git a/llvm/include/llvm/IR/ModuleSummaryIndex.h b/llvm/include/llvm/IR/ModuleSummaryIndex.h
--- a/llvm/include/llvm/IR/ModuleSummaryIndex.h
+++ b/llvm/include/llvm/IR/ModuleSummaryIndex.h
@@ -994,6 +994,13 @@
       : HaveGVs(HaveGVs), EnableSplitLTOUnit(EnableSplitLTOUnit), Saver(Alloc) {
   }
 
+  // Current version for the module summary in bitcode files.
+  // The BitcodeSummaryVersion should be bumped whenever we introduce changes
+  // in the way some record are interpreted, like flags for instance.
+  // Note that incrementing this may require changes in both BitcodeReader.cpp
+  // and BitcodeWriter.cpp.
+  static constexpr uint64_t BitcodeSummaryVersion = 8;
+
   bool haveGVs() const { return HaveGVs; }
 
   gvsummary_iterator begin() { return GlobalValueMap.begin(); }
diff --git a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
--- a/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
+++ b/llvm/lib/Bitcode/Reader/BitcodeReader.cpp
@@ -5778,9 +5778,11 @@
   }
   const uint64_t Version = Record[0];
   const bool IsOldProfileFormat = Version == 1;
-  if (Version < 1 || Version > 8)
+  if (Version < 1 || Version > ModuleSummaryIndex::BitcodeSummaryVersion)
     return error("Invalid summary version " + Twine(Version) +
-                 ". Version should be in the range [1-7].");
+                 ". Version should be in the range [1-" +
+                 Twine(ModuleSummaryIndex::BitcodeSummaryVersion) +
+                 "].");
   Record.clear();
 
   // Keep around the last seen summary to be used when we see an optional
diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
--- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
+++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp
@@ -3725,11 +3725,6 @@
   NameVals.clear();
 }
 
-// Current version for the summary.
-// This is bumped whenever we introduce changes in the way some record are
-// interpreted, like flags for instance.
-static const uint64_t INDEX_VERSION = 8;
-
 /// Emit the per-module summary section alongside the rest of
 /// the module's bitcode.
 void ModuleBitcodeWriterBase::writePerModuleGlobalValueSummary() {
@@ -3743,7 +3738,9 @@
                                  : bitc::FULL_LTO_GLOBALVAL_SUMMARY_BLOCK_ID,
                        4);
 
-  Stream.EmitRecord(bitc::FS_VERSION, ArrayRef<uint64_t>{INDEX_VERSION});
+  Stream.EmitRecord(
+      bitc::FS_VERSION,
+      ArrayRef<uint64_t>{ModuleSummaryIndex::BitcodeSummaryVersion});
 
   // Write the index flags.
   uint64_t Flags = 0;
@@ -3890,7 +3887,9 @@
 /// Emit the combined summary section into the combined index file.
 void IndexBitcodeWriter::writeCombinedGlobalValueSummary() {
   Stream.EnterSubblock(bitc::GLOBALVAL_SUMMARY_BLOCK_ID, 3);
-  Stream.EmitRecord(bitc::FS_VERSION, ArrayRef<uint64_t>{INDEX_VERSION});
+  Stream.EmitRecord(
+      bitc::FS_VERSION,
+      ArrayRef<uint64_t>{ModuleSummaryIndex::BitcodeSummaryVersion});
 
   // Write the index flags.
   uint64_t Flags = 0;
diff --git a/llvm/lib/IR/ModuleSummaryIndex.cpp b/llvm/lib/IR/ModuleSummaryIndex.cpp
--- a/llvm/lib/IR/ModuleSummaryIndex.cpp
+++ b/llvm/lib/IR/ModuleSummaryIndex.cpp
@@ -61,6 +61,8 @@
   return {RORefCnt, WORefCnt};
 }
 
+constexpr uint64_t ModuleSummaryIndex::BitcodeSummaryVersion;
+
 // Collect for the given module the list of function it defines
 // (GUID -> Summary).
 void ModuleSummaryIndex::collectDefinedFunctionsForModule(