diff --git a/llvm/lib/Transforms/Scalar/NaryReassociate.cpp b/llvm/lib/Transforms/Scalar/NaryReassociate.cpp
index 39720672c202d..3b3f32a0ea591 100644
--- a/llvm/lib/Transforms/Scalar/NaryReassociate.cpp
+++ b/llvm/lib/Transforms/Scalar/NaryReassociate.cpp
@@ -402,16 +402,17 @@ NaryReassociatePass::tryReassociateGEPAtIndex(GetElementPtrInst *GEP,
     IndexExprs.push_back(SE->getSCEV(Index));
   // Replace the I-th index with LHS.
   IndexExprs[I] = SE->getSCEV(LHS);
+  Type *GEPArgType = SE->getEffectiveSCEVType(GEP->getOperand(I)->getType());
+  Type *LHSType = SE->getEffectiveSCEVType(LHS->getType());
+  size_t LHSSize = DL->getTypeSizeInBits(LHSType).getFixedValue();
+  size_t GEPArgSize = DL->getTypeSizeInBits(GEPArgType).getFixedValue();
   if (isKnownNonNegative(LHS, SimplifyQuery(*DL, DT, AC, GEP)) &&
-      DL->getTypeSizeInBits(LHS->getType()).getFixedValue() <
-          DL->getTypeSizeInBits(GEP->getOperand(I)->getType())
-              .getFixedValue()) {
+      LHSSize < GEPArgSize) {
     // Zero-extend LHS if it is non-negative. InstCombine canonicalizes sext to
     // zext if the source operand is proved non-negative. We should do that
     // consistently so that CandidateExpr more likely appears before. See
     // @reassociate_gep_assume for an example of this canonicalization.
-    IndexExprs[I] =
-        SE->getZeroExtendExpr(IndexExprs[I], GEP->getOperand(I)->getType());
+    IndexExprs[I] = SE->getZeroExtendExpr(IndexExprs[I], GEPArgType);
   }
   const SCEV *CandidateExpr = SE->getGEPExpr(cast<GEPOperator>(GEP),
                                              IndexExprs);
diff --git a/llvm/test/Transforms/NaryReassociate/nary-gep.ll b/llvm/test/Transforms/NaryReassociate/nary-gep.ll
index d0ece1e11de5a..b56fdbe4a0669 100644
--- a/llvm/test/Transforms/NaryReassociate/nary-gep.ll
+++ b/llvm/test/Transforms/NaryReassociate/nary-gep.ll
@@ -21,6 +21,17 @@ define void @no_sext_fat_pointer(ptr addrspace(2) %a, i32 %i, i32 %j) {
   ret void
 }
 
+define ptr addrspace(2) @zext_fat_pointer_crash(ptr addrspace(2) %p, i32 %a) {
+; CHECK-LABEL: @zext_fat_pointer_crash(
+; CHECK-NEXT:    [[C:%.*]] = add i32 [[A:%.*]], 1
+; CHECK-NEXT:    [[Q:%.*]] = getelementptr double, ptr addrspace(2) [[P:%.*]], i32 [[C]]
+; CHECK-NEXT:    ret ptr addrspace(2) [[Q]]
+;
+  %c = add i32 %a, 1
+  %q = getelementptr double, ptr addrspace(2) %p, i32 %c
+  ret ptr addrspace(2) %q
+}
+
 define void @or_disjoint(ptr addrspace(2) %a, i32 %i, i32 %j, i32 %k) {
 ; CHECK-LABEL: @or_disjoint(
 ; CHECK-NEXT:    [[OR:%.*]] = or disjoint i32 [[I:%.*]], [[J:%.*]]