Index: clang/lib/Serialization/ASTReader.cpp
===================================================================
--- clang/lib/Serialization/ASTReader.cpp
+++ clang/lib/Serialization/ASTReader.cpp
@@ -4863,10 +4863,11 @@
       if (!NeedsImports)
         break;
 
-      unsigned Idx = 0, N = Record.size();
-      while (Idx < N) {
+      // Kind, ImportLoc, Size, ModTime, Signature
+      unsigned chunkSize = 1+1+1+1+5;
+      unsigned N = Record.size();
+      for (unsigned Idx = chunkSize; Idx < N; Idx += chunkSize) {
         // Read information about the AST file.
-        Idx += 1+1+1+1+5; // Kind, ImportLoc, Size, ModTime, Signature
         std::string ModuleName = ReadString(Record, Idx);
         std::string Filename = ReadString(Record, Idx);
         ResolveImportedPath(Filename, ModuleDir);