diff --git a/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/mapper/InferenceResultFieldMapper.java b/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/mapper/InferenceResultFieldMapper.java
index 4988734400330..dcb5c86b5eff7 100644
--- a/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/mapper/InferenceResultFieldMapper.java
+++ b/x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/mapper/InferenceResultFieldMapper.java
@@ -363,6 +363,7 @@ public SourceLoader.SyntheticFieldLoader syntheticFieldLoader() {
         return SourceLoader.SyntheticFieldLoader.NOTHING;
     }
 
+    @SuppressWarnings("unchecked")
     public static void applyFieldInference(
         Map<String, Object> inferenceMap,
         String field,
@@ -387,9 +388,10 @@ public static void applyFieldInference(
                 results.getWriteableName()
             );
         }
-        Map<String, Object> fieldMap = new LinkedHashMap<>();
+
+        Map<String, Object> fieldMap = (Map<String, Object>) inferenceMap.computeIfAbsent(field, s -> new LinkedHashMap<>());
         fieldMap.putAll(new SemanticTextModelSettings(model).asMap());
-        fieldMap.put(InferenceResultFieldMapper.RESULTS, chunks);
-        inferenceMap.put(field, fieldMap);
+        List<Map<String, Object>> fieldChunks = (List<Map<String, Object>>) fieldMap.computeIfAbsent(InferenceResultFieldMapper.RESULTS, k -> new ArrayList<>());
+        fieldChunks.addAll(chunks);
     }
 }
diff --git a/x-pack/plugin/inference/src/yamlRestTest/resources/rest-api-spec/test/inference/10_semantic_text_inference.yml b/x-pack/plugin/inference/src/yamlRestTest/resources/rest-api-spec/test/inference/10_semantic_text_inference.yml
index b22df64e83622..7f3107110c621 100644
--- a/x-pack/plugin/inference/src/yamlRestTest/resources/rest-api-spec/test/inference/10_semantic_text_inference.yml
+++ b/x-pack/plugin/inference/src/yamlRestTest/resources/rest-api-spec/test/inference/10_semantic_text_inference.yml
@@ -343,3 +343,38 @@ setup:
   - exists: _source._inference.top_level_field\.semantic_multifield.results.0.inference
 
 
+---
+"semantic_text copy_to calculate inference for source fields":
+  - do:
+      indices.create:
+        index: test-copy-to-index
+        body:
+          mappings:
+            properties:
+              inference_field:
+                type: semantic_text
+                model_id: dense-inference-id
+              source_field:
+                type: text
+                copy_to: inference_field
+
+  - do:
+      index:
+        index: test-copy-to-index
+        id: doc_1
+        body:
+          source_field: "copy_to inference test"
+          inference_field: "inference test"
+
+  - do:
+      get:
+        index: test-copy-to-index
+        id: doc_1
+
+  - match: { _source.inference_field: "inference test" }
+  - length: {_source._inference.inference_field.results: 2}
+  - match: { _source._inference.inference_field.results.0.text: "inference test" }
+  - match: { _source._inference.inference_field.results.1.text: "copy_to inference test" }
+
+  - exists: _source._inference.inference_field.results.0.inference
+  - exists: _source._inference.inference_field.results.1.inference