diff --git a/ansys/api/additive/VERSION b/ansys/api/additive/VERSION
index 2644290..fbcf992 100644
--- a/ansys/api/additive/VERSION
+++ b/ansys/api/additive/VERSION
@@ -1 +1 @@
-5.1.0-dev0
\ No newline at end of file
+5.1.1-dev0
\ No newline at end of file
diff --git a/ansys/api/additive/v0/additive_domain.proto b/ansys/api/additive/v0/additive_domain.proto
index b4770da..dc9b5b6 100644
--- a/ansys/api/additive/v0/additive_domain.proto
+++ b/ansys/api/additive/v0/additive_domain.proto
@@ -16,7 +16,7 @@ message MachineSettings {
     double layer_rotation_angle = 7;
     double hatch_spacing = 8;
     double slicing_stripe_width = 9;
-    string heat_source_model = 10;
+    HeatSourceModelType heat_source_model = 10;
     RingModeCoefficientSets ring_mode_coefficient_set = 11;
 }
 
@@ -307,6 +307,11 @@ message DownloadFileResponse {
 	Progress progress = 10;	// download progress
 }
 
+enum HeatSourceModelType {
+    HEAT_SOURCE_MODEL_GAUSSIAN = 0;
+    HEAT_SOURCE_MODEL_RING = 1;
+}
+
 enum RingModeCoefficientSets {
     RING_MODE_COEFFICIENT_SET_00 = 0;
     RING_MODE_COEFFICIENT_SET_01 = 1;