gatling.conf Could not resolve substitution to a value

Hi Folks,

I migrated to Gatling 3.4.1 from 2.x and am facing a strange issue. I used to pass a system property from the maven command line ( and used to refer in gatlin.conf as value to one of the keys (For example file = ${}/abc.txt).

After upgrade to 3.x, this doesn’t work anymore and simulation fails at startup with the following error

[main] ERROR io.gatling.compiler.ZincCompiler$ - Compilation crashed com.typesafe.config.ConfigException$UnresolvedSubstitution: gatling.conf @ file:/usr/local/perf-test/src/test/resources/gatling.conf: 64: Could not resolve substitution to a value: ${}

Any idea why it’s not working any more? Am I missing anything?


From this group’s terms:

  • Provide a Short, Self Contained, Correct (Compilable), Example (see

Hi Stephane, here are two github repos

  1. gatling2: This repo is using Gatling 2.x and I’ve added details in Here the system property value passed on command line ( is successfully substituted for the key defined in gatling.conf and log message show the substituted value
  2. gatling3: This repo is using Gatling 3.x and I’ve added details in with exception stacktrace.

Hope this helps.

Fixed, thanks for reporting:

That was really quick Stephane, thanks. The release date for 3.5.0 is already known?

In 2 weeks.