diff --git a/main/src/main/scala/sbt/Defaults.scala b/main/src/main/scala/sbt/Defaults.scala
index 97bce5bf5..b9eb595c6 100755
--- a/main/src/main/scala/sbt/Defaults.scala
+++ b/main/src/main/scala/sbt/Defaults.scala
@@ -471,13 +471,6 @@ object Defaults extends BuildCommon {
 
   // This is included into JvmPlugin.projectSettings
   def compileBase = inTask(console)(compilersSetting :: Nil) ++ compileBaseGlobal ++ Seq(
-    incOptions := incOptions.value
-      .withClassfileManagerType(
-        Option(
-          TransactionalManagerType
-            .of(crossTarget.value / "classes.bak", sbt.util.Logger.Null): ClassFileManagerType
-        ).toOptional
-      ),
     scalaInstance := scalaInstanceTask.value,
     crossVersion := (if (crossPaths.value) CrossVersion.binary else CrossVersion.disabled),
     sbtBinaryVersion in pluginCrossBuild := binarySbtVersion(
@@ -657,7 +650,20 @@ object Defaults extends BuildCommon {
       prev + (version -> (dependencyClasspathFiles / outputFileStamps).value)
     },
     compileBinaryFileInputs := compileBinaryFileInputs.triggeredBy(compile).value,
-    incOptions := { incOptions.value.withExternalHooks(externalHooks.value) },
+    incOptions := {
+      val old = incOptions.value
+      old
+        .withExternalHooks(externalHooks.value)
+        .withClassfileManagerType(
+          Option(
+            TransactionalManagerType
+              .of( // https://github.com/sbt/sbt/issues/1673
+                crossTarget.value / s"${prefix(configuration.value.name)}classes.bak",
+                sbt.util.Logger.Null
+              ): ClassFileManagerType
+          ).toOptional
+        )
+    },
     compileIncSetup := compileIncSetupTask.value,
     console := consoleTask.value,
     collectAnalyses := Definition.collectAnalysesTask.map(_ => ()).value,
diff --git a/sbt/src/sbt-test/tests/bak/build.sbt b/sbt/src/sbt-test/tests/bak/build.sbt
new file mode 100644
index 000000000..40b598c48
--- /dev/null
+++ b/sbt/src/sbt-test/tests/bak/build.sbt
@@ -0,0 +1,45 @@
+// https://github.com/sbt/sbt/issues/1673#issuecomment-537327439
+
+val Config_0 = config("config-0").extend(Compile)
+val Config_1 = config("config-1").extend(Compile)
+val Config_2 = config("config-2").extend(Compile)
+val Config_3 = config("config-3").extend(Compile)
+val Config_4 = config("config-4").extend(Compile)
+val Config_5 = config("config-5").extend(Compile)
+val Config_6 = config("config-6").extend(Compile)
+val Config_7 = config("config-7").extend(Compile)
+val Config_8 = config("config-8").extend(Compile)
+val Config_9 = config("config-9").extend(Compile)
+val Config_10 = config("config-10").extend(Compile)
+val Config_11 = config("config-11").extend(Compile)
+val Config_12 = config("config-12").extend(Compile)
+val Config_13 = config("config-13").extend(Compile)
+val Config_14 = config("config-14").extend(Compile)
+val Config_15 = config("config-15").extend(Compile)
+
+val CustomConfigs = List(Config_0, Config_1, Config_2, Config_3, Config_4, Config_5, Config_6, Config_7, Config_8, Config_9, Config_10, Config_11, Config_12, Config_13, Config_14, Config_15)
+
+val t = taskKey[Unit]("")
+val p1 = project
+  .configs(CustomConfigs: _*)
+  .settings(
+    t := {
+        (compile in Config_0).value
+        (compile in Config_1).value
+        (compile in Config_2).value
+        (compile in Config_3).value
+        (compile in Config_4).value
+        (compile in Config_5).value
+        (compile in Config_6).value
+        (compile in Config_7).value
+        (compile in Config_8).value
+        (compile in Config_9).value
+        (compile in Config_10).value
+        (compile in Config_11).value
+        (compile in Config_12).value
+        (compile in Config_13).value
+        (compile in Config_14).value
+        (compile in Config_15).value
+    }
+  )
+  .settings(CustomConfigs.flatMap(c => inConfig(c)(Defaults.testSettings)))
diff --git a/sbt/src/sbt-test/tests/bak/p1/src/config-0/scala/A.scala b/sbt/src/sbt-test/tests/bak/p1/src/config-0/scala/A.scala
new file mode 100644
index 000000000..3e19b86a5
--- /dev/null
+++ b/sbt/src/sbt-test/tests/bak/p1/src/config-0/scala/A.scala
@@ -0,0 +1,2 @@
+class A
+object A
diff --git a/sbt/src/sbt-test/tests/bak/p1/src/config-1/scala/A.scala b/sbt/src/sbt-test/tests/bak/p1/src/config-1/scala/A.scala
new file mode 100644
index 000000000..3e19b86a5
--- /dev/null
+++ b/sbt/src/sbt-test/tests/bak/p1/src/config-1/scala/A.scala
@@ -0,0 +1,2 @@
+class A
+object A
diff --git a/sbt/src/sbt-test/tests/bak/p1/src/config-10/scala/A.scala b/sbt/src/sbt-test/tests/bak/p1/src/config-10/scala/A.scala
new file mode 100644
index 000000000..3e19b86a5
--- /dev/null
+++ b/sbt/src/sbt-test/tests/bak/p1/src/config-10/scala/A.scala
@@ -0,0 +1,2 @@
+class A
+object A
diff --git a/sbt/src/sbt-test/tests/bak/p1/src/config-11/scala/A.scala b/sbt/src/sbt-test/tests/bak/p1/src/config-11/scala/A.scala
new file mode 100644
index 000000000..3e19b86a5
--- /dev/null
+++ b/sbt/src/sbt-test/tests/bak/p1/src/config-11/scala/A.scala
@@ -0,0 +1,2 @@
+class A
+object A
diff --git a/sbt/src/sbt-test/tests/bak/p1/src/config-12/scala/A.scala b/sbt/src/sbt-test/tests/bak/p1/src/config-12/scala/A.scala
new file mode 100644
index 000000000..3e19b86a5
--- /dev/null
+++ b/sbt/src/sbt-test/tests/bak/p1/src/config-12/scala/A.scala
@@ -0,0 +1,2 @@
+class A
+object A
diff --git a/sbt/src/sbt-test/tests/bak/p1/src/config-13/scala/A.scala b/sbt/src/sbt-test/tests/bak/p1/src/config-13/scala/A.scala
new file mode 100644
index 000000000..3e19b86a5
--- /dev/null
+++ b/sbt/src/sbt-test/tests/bak/p1/src/config-13/scala/A.scala
@@ -0,0 +1,2 @@
+class A
+object A
diff --git a/sbt/src/sbt-test/tests/bak/p1/src/config-14/scala/A.scala b/sbt/src/sbt-test/tests/bak/p1/src/config-14/scala/A.scala
new file mode 100644
index 000000000..3e19b86a5
--- /dev/null
+++ b/sbt/src/sbt-test/tests/bak/p1/src/config-14/scala/A.scala
@@ -0,0 +1,2 @@
+class A
+object A
diff --git a/sbt/src/sbt-test/tests/bak/p1/src/config-15/scala/A.scala b/sbt/src/sbt-test/tests/bak/p1/src/config-15/scala/A.scala
new file mode 100644
index 000000000..3e19b86a5
--- /dev/null
+++ b/sbt/src/sbt-test/tests/bak/p1/src/config-15/scala/A.scala
@@ -0,0 +1,2 @@
+class A
+object A
diff --git a/sbt/src/sbt-test/tests/bak/p1/src/config-2/scala/A.scala b/sbt/src/sbt-test/tests/bak/p1/src/config-2/scala/A.scala
new file mode 100644
index 000000000..3e19b86a5
--- /dev/null
+++ b/sbt/src/sbt-test/tests/bak/p1/src/config-2/scala/A.scala
@@ -0,0 +1,2 @@
+class A
+object A
diff --git a/sbt/src/sbt-test/tests/bak/p1/src/config-3/scala/A.scala b/sbt/src/sbt-test/tests/bak/p1/src/config-3/scala/A.scala
new file mode 100644
index 000000000..3e19b86a5
--- /dev/null
+++ b/sbt/src/sbt-test/tests/bak/p1/src/config-3/scala/A.scala
@@ -0,0 +1,2 @@
+class A
+object A
diff --git a/sbt/src/sbt-test/tests/bak/p1/src/config-4/scala/A.scala b/sbt/src/sbt-test/tests/bak/p1/src/config-4/scala/A.scala
new file mode 100644
index 000000000..3e19b86a5
--- /dev/null
+++ b/sbt/src/sbt-test/tests/bak/p1/src/config-4/scala/A.scala
@@ -0,0 +1,2 @@
+class A
+object A
diff --git a/sbt/src/sbt-test/tests/bak/p1/src/config-5/scala/A.scala b/sbt/src/sbt-test/tests/bak/p1/src/config-5/scala/A.scala
new file mode 100644
index 000000000..3e19b86a5
--- /dev/null
+++ b/sbt/src/sbt-test/tests/bak/p1/src/config-5/scala/A.scala
@@ -0,0 +1,2 @@
+class A
+object A
diff --git a/sbt/src/sbt-test/tests/bak/p1/src/config-6/scala/A.scala b/sbt/src/sbt-test/tests/bak/p1/src/config-6/scala/A.scala
new file mode 100644
index 000000000..3e19b86a5
--- /dev/null
+++ b/sbt/src/sbt-test/tests/bak/p1/src/config-6/scala/A.scala
@@ -0,0 +1,2 @@
+class A
+object A
diff --git a/sbt/src/sbt-test/tests/bak/p1/src/config-7/scala/A.scala b/sbt/src/sbt-test/tests/bak/p1/src/config-7/scala/A.scala
new file mode 100644
index 000000000..3e19b86a5
--- /dev/null
+++ b/sbt/src/sbt-test/tests/bak/p1/src/config-7/scala/A.scala
@@ -0,0 +1,2 @@
+class A
+object A
diff --git a/sbt/src/sbt-test/tests/bak/p1/src/config-8/scala/A.scala b/sbt/src/sbt-test/tests/bak/p1/src/config-8/scala/A.scala
new file mode 100644
index 000000000..3e19b86a5
--- /dev/null
+++ b/sbt/src/sbt-test/tests/bak/p1/src/config-8/scala/A.scala
@@ -0,0 +1,2 @@
+class A
+object A
diff --git a/sbt/src/sbt-test/tests/bak/p1/src/config-9/scala/A.scala b/sbt/src/sbt-test/tests/bak/p1/src/config-9/scala/A.scala
new file mode 100644
index 000000000..3e19b86a5
--- /dev/null
+++ b/sbt/src/sbt-test/tests/bak/p1/src/config-9/scala/A.scala
@@ -0,0 +1,2 @@
+class A
+object A
diff --git a/sbt/src/sbt-test/tests/bak/p1/src/main/java/p1/J.java b/sbt/src/sbt-test/tests/bak/p1/src/main/java/p1/J.java
new file mode 100644
index 000000000..3447cf9f3
--- /dev/null
+++ b/sbt/src/sbt-test/tests/bak/p1/src/main/java/p1/J.java
@@ -0,0 +1 @@
+package p1;
diff --git a/sbt/src/sbt-test/tests/bak/p1/src/main/scala/p1/A.scala b/sbt/src/sbt-test/tests/bak/p1/src/main/scala/p1/A.scala
new file mode 100644
index 000000000..accef61c7
--- /dev/null
+++ b/sbt/src/sbt-test/tests/bak/p1/src/main/scala/p1/A.scala
@@ -0,0 +1,4 @@
+package p1
+
+class A
+object A
diff --git a/sbt/src/sbt-test/tests/bak/p1/src/test/java/p1/J.java b/sbt/src/sbt-test/tests/bak/p1/src/test/java/p1/J.java
new file mode 100644
index 000000000..e69de29bb
diff --git a/sbt/src/sbt-test/tests/bak/p1/src/test/scala/p1/A.scala b/sbt/src/sbt-test/tests/bak/p1/src/test/scala/p1/A.scala
new file mode 100644
index 000000000..e69de29bb
diff --git a/sbt/src/sbt-test/tests/bak/test b/sbt/src/sbt-test/tests/bak/test
new file mode 100644
index 000000000..5a2768534
--- /dev/null
+++ b/sbt/src/sbt-test/tests/bak/test
@@ -0,0 +1,3 @@
+> p1/t;clean;p1/t;clean;p1/t;clean
+$ sleep 100
+> p1/t;clean;p1/t;clean;p1/t;clean