diff --git a/main/src/main/scala/sbt/Cross.scala b/main/src/main/scala/sbt/Cross.scala
index 5d3de17c0..dcff5d449 100644
--- a/main/src/main/scala/sbt/Cross.scala
+++ b/main/src/main/scala/sbt/Cross.scala
@@ -216,12 +216,30 @@ object Cross {
     Command.arb(requireSession(switchParser), switchHelp)(switchCommandImpl)
 
   private def switchCommandImpl(state: State, args: Switch): State = {
-    val switchedState = switchScalaVersion(args, state)
+    val x = Project.extract(state)
+    val (switchedState, affectedRefs) = switchScalaVersion(args, state)
 
-    args.command.toList ::: switchedState
+    val strictCmd =
+      if (args.version.force) {
+        // The Scala version was forced on the whole build, run as is
+        args.command
+      } else {
+        args.command.map { rawCmd =>
+          parseCommand(rawCmd) match {
+            case Right(_) => rawCmd // A project is specified, run as is
+            case Left(cmd) =>
+              resolveAggregates(x)
+                .intersect(affectedRefs)
+                .collect { case ProjectRef(_, proj) => s"$proj/$cmd" }
+                .mkString("all ", " ", "")
+          }
+        }
+      }
+
+    strictCmd.toList ::: switchedState
   }
 
-  private def switchScalaVersion(switch: Switch, state: State): State = {
+  private def switchScalaVersion(switch: Switch, state: State): (State, Seq[ResolvedReference]) = {
     val extracted = Project.extract(state)
     import extracted._
 
@@ -291,7 +309,7 @@ object Cross {
       }
     }
 
-    setScalaVersionForProjects(version, instance, projects, state, extracted)
+    (setScalaVersionForProjects(version, instance, projects, state, extracted), projects.map(_._1))
   }
 
   private def setScalaVersionForProjects(
diff --git a/notes/1.2.0/cross-strict-aggregation.md b/notes/1.2.0/cross-strict-aggregation.md
new file mode 100644
index 000000000..170207536
--- /dev/null
+++ b/notes/1.2.0/cross-strict-aggregation.md
@@ -0,0 +1,8 @@
+[@ruippeixotog]: https://github.com/ruippeixotog
+
+[#3698]: https://github.com/sbt/sbt/issues/3698
+[#3995]: https://github.com/sbt/sbt/pull/3995
+
+### Improvements
+
+- Make `++ <scala-version> <command>` run `<command>` only on compatible subprojects. [#3698][]/[#3995][] by [@ruippeixotog][]
diff --git a/sbt/src/sbt-test/actions/cross-strict-aggregation/build.sbt b/sbt/src/sbt-test/actions/cross-strict-aggregation/build.sbt
new file mode 100644
index 000000000..6c9759d4b
--- /dev/null
+++ b/sbt/src/sbt-test/actions/cross-strict-aggregation/build.sbt
@@ -0,0 +1,13 @@
+lazy val root = (project in file("."))
+  .aggregate(core, module)
+
+lazy val core = (project in file("core"))
+  .settings(
+    scalaVersion := "2.12.4",
+    crossScalaVersions := Seq("2.11.11", "2.12.4"))
+
+lazy val module = (project in file("module"))
+  .dependsOn(core)
+  .settings(
+    scalaVersion := "2.12.4",
+    crossScalaVersions := Seq("2.12.4"))
diff --git a/sbt/src/sbt-test/actions/cross-strict-aggregation/core/A.scala b/sbt/src/sbt-test/actions/cross-strict-aggregation/core/A.scala
new file mode 100644
index 000000000..6c542aa30
--- /dev/null
+++ b/sbt/src/sbt-test/actions/cross-strict-aggregation/core/A.scala
@@ -0,0 +1,5 @@
+package foo
+
+object Foo {
+
+}
diff --git a/sbt/src/sbt-test/actions/cross-strict-aggregation/module/B.scala b/sbt/src/sbt-test/actions/cross-strict-aggregation/module/B.scala
new file mode 100644
index 000000000..d262f7e5d
--- /dev/null
+++ b/sbt/src/sbt-test/actions/cross-strict-aggregation/module/B.scala
@@ -0,0 +1,5 @@
+package foo.module
+
+object FooModule {
+
+}
diff --git a/sbt/src/sbt-test/actions/cross-strict-aggregation/test b/sbt/src/sbt-test/actions/cross-strict-aggregation/test
new file mode 100644
index 000000000..fb3a4d9cb
--- /dev/null
+++ b/sbt/src/sbt-test/actions/cross-strict-aggregation/test
@@ -0,0 +1,5 @@
+> ++2.11.11 compile
+
+$ exists core/target/scala-2.11
+-$ exists module/target/scala-2.11
+-$ exists module/target/scala-2.12