diff --git a/docs/changelog/125446.yaml b/docs/changelog/125446.yaml
new file mode 100644
index 0000000000000..24a6ed6052fef
--- /dev/null
+++ b/docs/changelog/125446.yaml
@@ -0,0 +1,5 @@
+pr: 125446
+summary: Fix Semantic Text 8.x Upgrade Bug
+area: Mapping
+type: bug
+issues: []
diff --git a/server/src/main/java/org/elasticsearch/index/mapper/InferenceMetadataFieldsMapper.java b/server/src/main/java/org/elasticsearch/index/mapper/InferenceMetadataFieldsMapper.java
index 4039bccf1fd18..2dcd92be0952f 100644
--- a/server/src/main/java/org/elasticsearch/index/mapper/InferenceMetadataFieldsMapper.java
+++ b/server/src/main/java/org/elasticsearch/index/mapper/InferenceMetadataFieldsMapper.java
@@ -93,7 +93,9 @@ public static boolean isEnabled(Settings settings) {
         var version = IndexMetadata.SETTING_INDEX_VERSION_CREATED.get(settings);
         if ((version.before(IndexVersions.INFERENCE_METADATA_FIELDS)
             && version.between(IndexVersions.INFERENCE_METADATA_FIELDS_BACKPORT, IndexVersions.UPGRADE_TO_LUCENE_10_0_0) == false)
-            || (version.before(USE_NEW_SEMANTIC_TEXT_FORMAT_BY_DEFAULT) && USE_LEGACY_SEMANTIC_TEXT_FORMAT.exists(settings) == false)) {
+            || (version.onOrAfter(IndexVersions.UPGRADE_TO_LUCENE_10_0_0)
+                && version.before(USE_NEW_SEMANTIC_TEXT_FORMAT_BY_DEFAULT)
+                && USE_LEGACY_SEMANTIC_TEXT_FORMAT.exists(settings) == false)) {
             return false;
         }
 
diff --git a/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/mapper/SemanticInferenceMetadataFieldsMapperTests.java b/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/mapper/SemanticInferenceMetadataFieldsMapperTests.java
index f877b0182d888..23519ec86cbc4 100644
--- a/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/mapper/SemanticInferenceMetadataFieldsMapperTests.java
+++ b/x-pack/plugin/inference/src/test/java/org/elasticsearch/xpack/inference/mapper/SemanticInferenceMetadataFieldsMapperTests.java
@@ -71,6 +71,27 @@ public void testIsEnabledByDefault() {
             )
             .build();
         assertTrue(InferenceMetadataFieldsMapper.isEnabled(settings));
+
+        // Test upgrades from 8.x
+        settings = Settings.builder()
+            .put(
+                IndexMetadata.SETTING_INDEX_VERSION_CREATED.getKey(),
+                IndexVersionUtils.randomPreviousCompatibleVersion(random(), IndexVersions.INFERENCE_METADATA_FIELDS_BACKPORT)
+            )
+            .build();
+        assertFalse(InferenceMetadataFieldsMapper.isEnabled(settings));
+
+        settings = Settings.builder()
+            .put(
+                IndexMetadata.SETTING_INDEX_VERSION_CREATED.getKey(),
+                IndexVersionUtils.randomVersionBetween(
+                    random(),
+                    IndexVersions.INFERENCE_METADATA_FIELDS_BACKPORT,
+                    IndexVersionUtils.getPreviousVersion(IndexVersions.UPGRADE_TO_LUCENE_10_0_0)
+                )
+            )
+            .build();
+        assertTrue(InferenceMetadataFieldsMapper.isEnabled(settings));
     }
 
     @Override