diff --git a/akka-stream/src/main/scala/akka/stream/javadsl/Flow.scala b/akka-stream/src/main/scala/akka/stream/javadsl/Flow.scala
index 7dd910b08c..79d512fb78 100755
--- a/akka-stream/src/main/scala/akka/stream/javadsl/Flow.scala
+++ b/akka-stream/src/main/scala/akka/stream/javadsl/Flow.scala
@@ -454,7 +454,7 @@ final class Flow[In, Out, Mat](delegate: scaladsl.Flow[In, Out, Mat]) extends Gr
    * | Resulting Flow            |
    * |                           |
    * | +------+        +------+  |
-   * | |      | ~Out~> |      | ~~> O2
+   * | |      | ~Out~> |      | ~~> O1
    * | | flow |        | bidi |  |
    * | |      | <~In~  |      | <~~ I2
    * | +------+        +------+  |
@@ -464,7 +464,7 @@ final class Flow[In, Out, Mat](delegate: scaladsl.Flow[In, Out, Mat]) extends Gr
    * value of the current flow (ignoring the [[BidiFlow]]’s value), use
    * [[Flow#joinMat[I2* joinMat]] if a different strategy is needed.
    */
-  def join[I2, O2, Mat2](bidi: Graph[BidiShape[Out, O2, I2, In], Mat2]): Flow[I2, O2, Mat] =
+  def join[I2, O1, Mat2](bidi: Graph[BidiShape[Out, O1, I2, In], Mat2]): Flow[I2, O1, Mat] =
     new Flow(delegate.join(bidi))
 
   /**
@@ -474,7 +474,7 @@ final class Flow[In, Out, Mat](delegate: scaladsl.Flow[In, Out, Mat]) extends Gr
    * | Resulting Flow            |
    * |                           |
    * | +------+        +------+  |
-   * | |      | ~Out~> |      | ~~> O2
+   * | |      | ~Out~> |      | ~~> O1
    * | | flow |        | bidi |  |
    * | |      | <~In~  |      | <~~ I2
    * | +------+        +------+  |
@@ -488,9 +488,9 @@ final class Flow[In, Out, Mat](delegate: scaladsl.Flow[In, Out, Mat]) extends Gr
    *
    * See also [[viaMat]] when access to materialized values of the parameter is needed.
    */
-  def joinMat[I2, O2, Mat2, M](
-      bidi: Graph[BidiShape[Out, O2, I2, In], Mat2],
-      combine: function.Function2[Mat, Mat2, M]): Flow[I2, O2, M] =
+  def joinMat[I2, O1, Mat2, M](
+      bidi: Graph[BidiShape[Out, O1, I2, In], Mat2],
+      combine: function.Function2[Mat, Mat2, M]): Flow[I2, O1, M] =
     new Flow(delegate.joinMat(bidi)(combinerToScala(combine)))
 
   /**
diff --git a/akka-stream/src/main/scala/akka/stream/scaladsl/Flow.scala b/akka-stream/src/main/scala/akka/stream/scaladsl/Flow.scala
index 5eaea9903d..84b9be867c 100755
--- a/akka-stream/src/main/scala/akka/stream/scaladsl/Flow.scala
+++ b/akka-stream/src/main/scala/akka/stream/scaladsl/Flow.scala
@@ -188,7 +188,7 @@ final class Flow[-In, +Out, +Mat](
    * | Resulting Flow            |
    * |                           |
    * | +------+        +------+  |
-   * | |      | ~Out~> |      | ~~> O2
+   * | |      | ~Out~> |      | ~~> O1
    * | | flow |        | bidi |  |
    * | |      | <~In~  |      | <~~ I2
    * | +------+        +------+  |
@@ -198,7 +198,7 @@ final class Flow[-In, +Out, +Mat](
    * value of the current flow (ignoring the [[BidiFlow]]’s value), use
    * [[Flow#joinMat[I2* joinMat]] if a different strategy is needed.
    */
-  def join[I2, O2, Mat2](bidi: Graph[BidiShape[Out, O2, I2, In], Mat2]): Flow[I2, O2, Mat] = joinMat(bidi)(Keep.left)
+  def join[I2, O1, Mat2](bidi: Graph[BidiShape[Out, O1, I2, In], Mat2]): Flow[I2, O1, Mat] = joinMat(bidi)(Keep.left)
 
   /**
    * Join this [[Flow]] to a [[BidiFlow]] to close off the “top” of the protocol stack:
@@ -207,7 +207,7 @@ final class Flow[-In, +Out, +Mat](
    * | Resulting Flow            |
    * |                           |
    * | +------+        +------+  |
-   * | |      | ~Out~> |      | ~~> O2
+   * | |      | ~Out~> |      | ~~> O1
    * | | flow |        | bidi |  |
    * | |      | <~In~  |      | <~~ I2
    * | +------+        +------+  |
@@ -219,8 +219,8 @@ final class Flow[-In, +Out, +Mat](
    * It is recommended to use the internally optimized `Keep.left` and `Keep.right` combiners
    * where appropriate instead of manually writing functions that pass through one of the values.
    */
-  def joinMat[I2, O2, Mat2, M](bidi: Graph[BidiShape[Out, O2, I2, In], Mat2])(
-      combine: (Mat, Mat2) => M): Flow[I2, O2, M] = {
+  def joinMat[I2, O1, Mat2, M](bidi: Graph[BidiShape[Out, O1, I2, In], Mat2])(
+      combine: (Mat, Mat2) => M): Flow[I2, O1, M] = {
     val newBidiShape = bidi.shape.deepCopy()
     val newFlowShape = shape.deepCopy()