Ruby Gotcha: Environment Variables Are Always Strings

Fri, 10 Jul 2026 00:00:00 +0000

I recently ran into a small but frustrating production bug caused by a common Ruby mistake.

I had a feature controlled by an environment variable:

DISABLE_THING=false

The application restarted successfully, but the feature was still disabled.

The reason? In Ruby, environment variables are always strings.

ENV["DISABLE_THING"]
# => "false"

And in Ruby, a non-empty string is truthy.

if "false"
  puts "This runs!"
end

# This runs!

So even though the value looks like false, Ruby sees it as a string containing five characters, not the boolean value false.

Feature-Flags on Saroj Maharjan