diff --git a/CHANGELOG.md b/CHANGELOG.md
index 787618dec..f055c6e1c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,9 @@ Note that Sockeye has checks in place to not translate with an old model that wa
 
 Each version section may have have subsections for: _Added_, _Changed_, _Removed_, _Deprecated_, and _Fixed_.
 
+## [1.18.71]
+- Fixed default setting of source factor combination to be 'concat' for backwards compatibility.
+
 ## [1.18.70]
 ### Added
 - Sockeye now outputs fields found in a JSON input object, if they are not overwritten by Sockeye. This behavior can be enabled by selecting `--json-input` (to read input as a JSON object) and `--output-type json` (to write a JSON object to output).
diff --git a/sockeye/__init__.py b/sockeye/__init__.py
index 563d7e6ff..db1b372a5 100644
--- a/sockeye/__init__.py
+++ b/sockeye/__init__.py
@@ -11,4 +11,4 @@
 # express or implied. See the License for the specific language governing
 # permissions and limitations under the License.
 
-__version__ = '1.18.70'
+__version__ = '1.18.71'
diff --git a/sockeye/encoder.py b/sockeye/encoder.py
index b15f6afd8..fd33a2504 100644
--- a/sockeye/encoder.py
+++ b/sockeye/encoder.py
@@ -338,7 +338,7 @@ def __init__(self,
                  num_embed: int,
                  dropout: float,
                  factor_configs: Optional[List[FactorConfig]] = None,
-                 source_factors_combine: str = C.SOURCE_FACTORS_COMBINE_SUM,
+                 source_factors_combine: str = C.SOURCE_FACTORS_COMBINE_CONCAT,
                  dtype: str = C.DTYPE_FP32) -> None:
         super().__init__()
         self.vocab_size = vocab_size