diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7d3738784..3721ca738 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Support for SPARK Pro 24.0 (eng/recordflux/RecordFlux#1409)
 
+### Fixed
+
+- User defined `GNATCOLL_ICONV_OPT` environment variable is ignored (AdaCore/RecordFlux#1289, eng/recordflux/RecordFlux#1437)
+
 ### Removed
 
 - Support for SPARK Pro Wavefront 20230905 (eng/recordflux/RecordFlux#1409)
diff --git a/setup.py b/setup.py
index 7abca5810..073c28ac1 100644
--- a/setup.py
+++ b/setup.py
@@ -27,7 +27,8 @@ def run(self) -> None:
                 "generated/adasat",
             ],
         )
-        env["GNATCOLL_ICONV_OPT"] = "-v"
+        if "GNATCOLL_ICONV_OPT" not in env:
+            env["GNATCOLL_ICONV_OPT"] = "-v"
         subprocess.run(
             [
                 "gprbuild",