diff --git a/llvm/lib/Transforms/AggressiveInstCombine/TruncInstCombine.cpp b/llvm/lib/Transforms/AggressiveInstCombine/TruncInstCombine.cpp
--- a/llvm/lib/Transforms/AggressiveInstCombine/TruncInstCombine.cpp
+++ b/llvm/lib/Transforms/AggressiveInstCombine/TruncInstCombine.cpp
@@ -281,8 +281,10 @@
 /// version of \p Ty, otherwise return \p Ty.
 static Type *getReducedType(Value *V, Type *Ty) {
   assert(Ty && !Ty->isVectorTy() && "Expect Scalar Type");
-  if (auto *VTy = dyn_cast<VectorType>(V->getType()))
-    return VectorType::get(Ty, VTy->getNumElements());
+  if (auto *VTy = dyn_cast<VectorType>(V->getType())) {
+    // FIXME: should this handle scalable vectors?
+    return FixedVectorType::get(Ty, VTy->getNumElements());
+  }
   return Ty;
 }