diff --git a/llvm/lib/IR/Operator.cpp b/llvm/lib/IR/Operator.cpp
--- a/llvm/lib/IR/Operator.cpp
+++ b/llvm/lib/IR/Operator.cpp
@@ -45,6 +45,11 @@
     if (OpC->isZero())
       continue;
 
+    // Scalable vectors have are multiplied by a runtime constant.
+    if (auto *VecTy = dyn_cast<VectorType>(GTI.getIndexedType()))
+      if (VecTy->isScalable())
+        return false;
+
     // Handle a struct index, which adds its field offset to the pointer.
     if (StructType *STy = GTI.getStructTypeOrNull()) {
       unsigned ElementIdx = OpC->getZExtValue();
diff --git a/llvm/test/Transforms/InstCombine/gep-vector.ll b/llvm/test/Transforms/InstCombine/gep-vector.ll
--- a/llvm/test/Transforms/InstCombine/gep-vector.ll
+++ b/llvm/test/Transforms/InstCombine/gep-vector.ll
@@ -134,3 +134,24 @@
   %gep = getelementptr inbounds [4 x i32], [4 x i32] addrspace(3)* %asc, i64 %y, i64 %z
   ret i32 addrspace(3)* %gep
 }
+
+; Negative test - avoid doing bitcast on i8*, because '16' should be scaled by 'vscale'.
+
+define i8* @test_accumulate_constant_offset_vscale_nonzero(<vscale x 16 x i1> %pg, i8* %base) {
+; CHECK-LABEL: @test_accumulate_constant_offset_vscale_nonzero
+; CHECK-NEXT:   %bc = bitcast i8* %base to <vscale x 16 x i8>*
+; CHECK-NEXT:   %gep = getelementptr <vscale x 16 x i8>, <vscale x 16 x i8>* %bc, i64 1, i64 4
+; CHECK-NEXT:   ret i8* %gep
+  %bc = bitcast i8* %base to <vscale x 16 x i8>*
+  %gep = getelementptr <vscale x 16 x i8>, <vscale x 16 x i8>* %bc, i64 1, i64 4
+  ret i8* %gep
+}
+
+define i8* @test_accumulate_constant_offset_vscale_zero(<vscale x 16 x i1> %pg, i8* %base) {
+; CHECK-LABEL: @test_accumulate_constant_offset_vscale_zero
+; CHECK-NEXT:   %[[RES:.*]] = getelementptr i8, i8* %base, i64 4
+; CHECK-NEXT:   ret i8* %[[RES]]
+  %bc = bitcast i8* %base to <vscale x 16 x i8>*
+  %gep = getelementptr <vscale x 16 x i8>, <vscale x 16 x i8>* %bc, i64 0, i64 4
+  ret i8* %gep
+}