diff --git a/build.sbt b/build.sbt
index 270d6376f..b66d8d227 100644
--- a/build.sbt
+++ b/build.sbt
@@ -1100,6 +1100,7 @@ lazy val sbtClientProj = (project in file("client"))
   .dependsOn(commandProj)
   .settings(
     commonBaseSettings,
+    scalaVersion := "2.12.11", // The thin client does not build with 2.12.12
     publish / skip := true,
     name := "sbt-client",
     mimaPreviousArtifacts := Set.empty,