diff --git a/govc/test/vm.bats b/govc/test/vm.bats
index a76c28c59..85c0576db 100755
--- a/govc/test/vm.bats
+++ b/govc/test/vm.bats
@@ -686,8 +686,15 @@ load test_helper
 
   run govc vm.disk.create -vm "$vm" -name "$vm/$name" -size 1M
   assert_success
-  result=$(govc device.ls -vm "$vm" | grep -c disk-)
+  disk=$(govc device.ls -vm "$vm" disk-* | awk '{print $1}')
+  result=$(grep -c disk- <<<"$disk")
   [ "$result" -eq 1 ]
+
+  run govc vm.disk.change -vm "$vm" -disk.name "$disk" -size 2M
+  assert_success
+
+  run govc vm.disk.change -vm "$vm" -disk.name "$disk" -size 1M
+  assert_failure # cannot shrink disk
 }
 
 @test "vm.disk.attach" {
diff --git a/govc/vm/disk/change.go b/govc/vm/disk/change.go
index e7203c9de..d57b1bd46 100644
--- a/govc/vm/disk/change.go
+++ b/govc/vm/disk/change.go
@@ -153,9 +153,13 @@ func (cmd *change) Run(ctx context.Context, f *flag.FlagSet) error {
 	}
 
 	if int64(cmd.bytes) != 0 {
-		editdisk.CapacityInKB = int64(cmd.bytes) / 1024
+		editdisk.CapacityInBytes = int64(cmd.bytes)
+		editdisk.CapacityInKB = int64(0) // zero deprecated field
 	}
 
+	if editdisk.StorageIOAllocation == nil {
+		editdisk.StorageIOAllocation = new(types.StorageIOAllocationInfo)
+	}
 	editdisk.StorageIOAllocation.Limit = cmd.limit
 
 	switch backing := editdisk.Backing.(type) {
diff --git a/simulator/virtual_machine.go b/simulator/virtual_machine.go
index 7f1929901..6fd4cc851 100644
--- a/simulator/virtual_machine.go
+++ b/simulator/virtual_machine.go
@@ -1184,7 +1184,10 @@ func getDiskSize(disk *types.VirtualDisk) int64 {
 
 func changedDiskSize(oldDisk *types.VirtualDisk, newDiskSpec *types.VirtualDisk) (int64, bool) {
 	// capacity cannot be decreased
-	if newDiskSpec.CapacityInBytes < oldDisk.CapacityInBytes || newDiskSpec.CapacityInKB < oldDisk.CapacityInKB {
+	if newDiskSpec.CapacityInBytes > 0 && newDiskSpec.CapacityInBytes < oldDisk.CapacityInBytes {
+		return 0, false
+	}
+	if newDiskSpec.CapacityInKB > 0 && newDiskSpec.CapacityInKB < oldDisk.CapacityInKB {
 		return 0, false
 	}
 
@@ -1196,10 +1199,13 @@ func changedDiskSize(oldDisk *types.VirtualDisk, newDiskSpec *types.VirtualDisk)
 		return newDiskSpec.CapacityInBytes, true
 	}
 
-	// CapacityInBytes and CapacityInKB indicate different values
-	if newDiskSpec.CapacityInBytes != newDiskSpec.CapacityInKB*1024 {
-		return 0, false
+	// if both set, CapacityInBytes and CapacityInKB must be the same
+	if newDiskSpec.CapacityInBytes > 0 && newDiskSpec.CapacityInKB > 0 {
+		if newDiskSpec.CapacityInBytes != newDiskSpec.CapacityInKB*1024 {
+			return 0, false
+		}
 	}
+
 	return newDiskSpec.CapacityInBytes, true
 }