diff --git a/modules/video_coding/video_codec_initializer.cc b/modules/video_coding/video_codec_initializer.cc
index 777056fb24..36401ff244 100644
--- a/modules/video_coding/video_codec_initializer.cc
+++ b/modules/video_coding/video_codec_initializer.cc
@@ -210,7 +210,7 @@ VideoCodec VideoCodecInitializer::VideoEncoderConfigToVideoCodec(
 
         for (size_t spatial_idx = first_active_layer;
              spatial_idx < config.simulcast_layers.size() &&
-             spatial_idx < spatial_layers.size();
+             spatial_idx < spatial_layers.size() + first_active_layer;
              ++spatial_idx) {
           spatial_layers[spatial_idx - first_active_layer].active =
               config.simulcast_layers[spatial_idx].active;
diff --git a/modules/video_coding/video_codec_initializer_unittest.cc b/modules/video_coding/video_codec_initializer_unittest.cc
index 686396c51a..1ea145e14f 100644
--- a/modules/video_coding/video_codec_initializer_unittest.cc
+++ b/modules/video_coding/video_codec_initializer_unittest.cc
@@ -364,24 +364,66 @@ TEST_F(VideoCodecInitializerTest, Vp9DeactivateLayers) {
   config_.simulcast_layers[1].active = true;
   config_.simulcast_layers[2].active = true;
   EXPECT_TRUE(InitializeCodec());
+  EXPECT_EQ(codec_out_.VP9()->numberOfSpatialLayers, 3);
   EXPECT_TRUE(codec_out_.spatialLayers[0].active);
   EXPECT_TRUE(codec_out_.spatialLayers[1].active);
   EXPECT_TRUE(codec_out_.spatialLayers[2].active);
 
   // Deactivate top layer.
+  config_.simulcast_layers[0].active = true;
+  config_.simulcast_layers[1].active = true;
   config_.simulcast_layers[2].active = false;
   EXPECT_TRUE(InitializeCodec());
+  EXPECT_EQ(codec_out_.VP9()->numberOfSpatialLayers, 3);
   EXPECT_TRUE(codec_out_.spatialLayers[0].active);
   EXPECT_TRUE(codec_out_.spatialLayers[1].active);
   EXPECT_FALSE(codec_out_.spatialLayers[2].active);
 
   // Deactivate middle layer.
-  config_.simulcast_layers[2].active = true;
+  config_.simulcast_layers[0].active = true;
   config_.simulcast_layers[1].active = false;
+  config_.simulcast_layers[2].active = true;
   EXPECT_TRUE(InitializeCodec());
+  EXPECT_EQ(codec_out_.VP9()->numberOfSpatialLayers, 3);
   EXPECT_TRUE(codec_out_.spatialLayers[0].active);
   EXPECT_FALSE(codec_out_.spatialLayers[1].active);
   EXPECT_TRUE(codec_out_.spatialLayers[2].active);
+
+  // Deactivate first layer.
+  config_.simulcast_layers[0].active = false;
+  config_.simulcast_layers[1].active = true;
+  config_.simulcast_layers[2].active = true;
+  EXPECT_TRUE(InitializeCodec());
+  EXPECT_EQ(codec_out_.VP9()->numberOfSpatialLayers, 2);
+  EXPECT_TRUE(codec_out_.spatialLayers[0].active);
+  EXPECT_TRUE(codec_out_.spatialLayers[1].active);
+
+  // HD singlecast.
+  config_.simulcast_layers[0].active = false;
+  config_.simulcast_layers[1].active = false;
+  config_.simulcast_layers[2].active = true;
+  EXPECT_TRUE(InitializeCodec());
+  EXPECT_EQ(codec_out_.VP9()->numberOfSpatialLayers, 1);
+  EXPECT_TRUE(codec_out_.spatialLayers[0].active);
+
+  // VGA singlecast.
+  config_.simulcast_layers[0].active = false;
+  config_.simulcast_layers[1].active = true;
+  config_.simulcast_layers[2].active = false;
+  EXPECT_TRUE(InitializeCodec());
+  EXPECT_EQ(codec_out_.VP9()->numberOfSpatialLayers, 2);
+  EXPECT_TRUE(codec_out_.spatialLayers[0].active);
+  EXPECT_FALSE(codec_out_.spatialLayers[1].active);
+
+  // QVGA singlecast.
+  config_.simulcast_layers[0].active = true;
+  config_.simulcast_layers[1].active = false;
+  config_.simulcast_layers[2].active = false;
+  EXPECT_TRUE(InitializeCodec());
+  EXPECT_EQ(codec_out_.VP9()->numberOfSpatialLayers, 3);
+  EXPECT_TRUE(codec_out_.spatialLayers[0].active);
+  EXPECT_FALSE(codec_out_.spatialLayers[1].active);
+  EXPECT_FALSE(codec_out_.spatialLayers[2].active);
 }
 
 }  // namespace webrtc