Parsing nix-env's performance statistics failed.

Parse error:
Error("expected ident", line: 1, column: 3)

Evaluation output:
trace: warning: chromium: stable version 76.0.3809.100 is newer than a patchset bounded at 72. You can safely delete it.
{
  "cpuTime": 161.744,
  "envs": {
    "number": 110793736,
    "elements": 167133968,
    "bytes": 3109771520
  },
  "list": {
    "elements": 201226082,
    "bytes": 1609808656,
    "concats": 7567811
  },
  "values": {
    "number": 234502822,
    "bytes": 5628067728
  },
  "symbols": {
    "number": 331937,
    "bytes": 15062540
  },
  "sets": {
    "number": 28610641,
    "bytes": 8094564272,
    "elements": 327736631
  },
  "sizes": {
    "Env": 16,
    "Value": 24,
    "Bindings": 8,
    "Attr": 24
  },
  "nrOpUpdates": 13365923,
  "nrOpUpdateValuesCopied": 240688371,
  "nrThunks": 160192569,
  "nrAvoided": 156089126,
  "nrLookups": 77800695,
  "nrPrimOpCalls": 67966929,
  "nrFunctionCalls": 96630947,
  "gc": {
    "heapSize": 12398817280,
    "totalBytes": 24166964272
  }
}