diff --git a/scalapb-runtime/build.sbt b/scalapb-runtime/build.sbt
index 1abf9cd45..bdb3f48fd 100644
--- a/scalapb-runtime/build.sbt
+++ b/scalapb-runtime/build.sbt
@@ -6,7 +6,7 @@ libraryDependencies ++= Seq(
   "com.google.protobuf" % "protobuf-java" % "3.0.0-alpha-3",
   "com.trueaccord.lenses" %% "lenses" % "0.4.1",
   "org.scalacheck" %% "scalacheck" % "1.12.4" % "test",
-  "org.scalatest" %% "scalatest" % "2.2.4" % "test"
+  "org.scalatest" %% "scalatest" % (if (scalaVersion.value.startsWith("2.12")) "2.2.5-M1" else "2.2.5") % "test"
 )
 
 unmanagedResourceDirectories in Compile += baseDirectory.value / "../protobuf"