diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -4471,7 +4471,16 @@
   // Note that we do not instantiate a definition until we see an odr-use
   // in DoMarkVarDeclReferenced().
   // FIXME: LateAttrs et al.?
-  VarTemplateSpecializationDecl *Decl = BuildVarTemplateInstantiation(
+  // Search for the variable template specialization declaration that
+  // corresponds to these arguments again to get an up-to-date InsertPos.
+  // The template argument deduction in between may update the underlying
+  // specialization container and invalidate previous iterators.
+  VarTemplateSpecializationDecl *Decl =
+      Template->findSpecialization(Converted, InsertPos);
+  // Assert we should not have a variable template specialization, otherwise we
+  // should have returned early.
+  assert(!Decl);
+  Decl = BuildVarTemplateInstantiation(
       Template, InstantiationPattern, *InstantiationArgs, TemplateArgs,
       Converted, TemplateNameLoc, InsertPos /*, LateAttrs, StartingScope*/);
   if (!Decl)