diff --git a/CHANGELOG.md b/CHANGELOG.md
index 07a5b4ad50e..c22223beff7 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -55,6 +55,7 @@
 * [#8517](https://github.com/rubocop-hq/rubocop/pull/8517): Make `Style/HashTransformKeys` and `Style/HashTransformValues` aware of `to_h` with block. ([@eugeneius][])
 * [#8529](https://github.com/rubocop-hq/rubocop/pull/8529): Mark `Lint/FrozenStringLiteralComment` as `Safe`, but with unsafe auto-correction. ([@marcandre][])
 * [#8602](https://github.com/rubocop-hq/rubocop/pull/8602): Fix usage of `to_enum(:scan, regexp)` to work on TruffleRuby. ([@jaimerave][])
+* [#8629](https://github.com/rubocop-hq/rubocop/pull/8629): Fix the cache being reusable in CI by using crc32 to calculate file hashes rather than `mtime`, which changes each CI build. ([@dvandersluis][])
 
 ## 0.89.1 (2020-08-10)
 
diff --git a/lib/rubocop/result_cache.rb b/lib/rubocop/result_cache.rb
index 2dda0c8a6fc..ebc8d7ab925 100644
--- a/lib/rubocop/result_cache.rb
+++ b/lib/rubocop/result_cache.rb
@@ -3,6 +3,7 @@
 require 'digest/sha1'
 require 'find'
 require 'etc'
+require 'zlib'
 
 module RuboCop
   # Provides functionality for caching rubocop runs.
@@ -171,7 +172,7 @@ def rubocop_checksum
           rubocop_extra_features
             .select { |path| File.file?(path) }
             .sort!
-            .each { |path| digest << File.mtime(path).to_s }
+            .each { |path| digest << Zlib.crc32(IO.read(path)).to_s }
           digest << RuboCop::Version::STRING << RuboCop::AST::Version::STRING
           digest.hexdigest
         end