diff --git a/src/lake/Lake/Config/LeanConfig.lean b/src/lake/Lake/Config/LeanConfig.lean
index f0dbc5c798..c4d67363e6 100644
--- a/src/lake/Lake/Config/LeanConfig.lean
+++ b/src/lake/Lake/Config/LeanConfig.lean
@@ -118,7 +118,7 @@ public def leancArgs : BuildType → Array String
 | release => #["-O3", "-DNDEBUG"]
 
 public def ofString? (s : String) : Option BuildType :=
-  match s with
+  match s.decapitalize with
   | "debug" => some .debug
   | "relWithDebInfo" => some .relWithDebInfo
   | "minSizeRel" => some .minSizeRel
diff --git a/src/lake/tests/translateConfig/source.toml b/src/lake/tests/translateConfig/source.toml
index b85095a0a3..f6f5cbeffc 100644
--- a/src/lake/tests/translateConfig/source.toml
+++ b/src/lake/tests/translateConfig/source.toml
@@ -16,7 +16,7 @@ releaseRepo = ""
 buildArchive = ""
 preferReleaseBuild = false
 packagesDir = ".lake/packages"
-buildType = "release"
+buildType = "Release"
 leanOptions = []
 moreServerOptions = []
 moreLeanArgs = []