diff --git a/crates/meilisearch/tests/vector/mod.rs b/crates/meilisearch/tests/vector/mod.rs
index 67da51702..2a7038fcb 100644
--- a/crates/meilisearch/tests/vector/mod.rs
+++ b/crates/meilisearch/tests/vector/mod.rs
@@ -100,7 +100,7 @@ async fn add_remove_user_provided() {
     let (documents, _code) = index
         .get_all_documents(GetAllDocumentsOptions { retrieve_vectors: true, ..Default::default() })
         .await;
-    snapshot!(json_string!(documents), @r###"
+    snapshot!(json_string!(documents), @r#"
     {
       "results": [
         {
@@ -134,7 +134,7 @@ async fn add_remove_user_provided() {
       "limit": 20,
       "total": 2
     }
-    "###);
+    "#);
 
     let (value, code) = index.delete_document(0).await;
     snapshot!(code, @"202 Accepted");
@@ -143,7 +143,7 @@ async fn add_remove_user_provided() {
     let (documents, _code) = index
         .get_all_documents(GetAllDocumentsOptions { retrieve_vectors: true, ..Default::default() })
         .await;
-    snapshot!(json_string!(documents), @r###"
+    snapshot!(json_string!(documents), @r#"
     {
       "results": [
         {
@@ -161,6 +161,97 @@ async fn add_remove_user_provided() {
       "limit": 20,
       "total": 1
     }
+    "#);
+}
+
+#[actix_rt::test]
+async fn user_provide_mismatched_embedding_dimension() {
+    let server = Server::new().await;
+    let index = server.index("doggo");
+
+    let (response, code) = index
+        .update_settings(json!({
+          "embedders": {
+              "manual": {
+                  "source": "userProvided",
+                  "dimensions": 3,
+              }
+          },
+        }))
+        .await;
+    snapshot!(code, @"202 Accepted");
+    server.wait_task(response.uid()).await.succeeded();
+
+    let documents = json!([
+      {"id": 0, "name": "kefir", "_vectors": { "manual": [0, 0] }},
+    ]);
+    let (value, code) = index.add_documents(documents, None).await;
+    snapshot!(code, @"202 Accepted");
+    let task = index.wait_task(value.uid()).await;
+    snapshot!(task, @r#"
+    {
+      "uid": "[uid]",
+      "batchUid": "[batch_uid]",
+      "indexUid": "doggo",
+      "status": "failed",
+      "type": "documentAdditionOrUpdate",
+      "canceledBy": null,
+      "details": {
+        "receivedDocuments": 1,
+        "indexedDocuments": 0
+      },
+      "error": {
+        "message": "Index `doggo`: Invalid vector dimensions: expected: `3`, found: `2`.",
+        "code": "invalid_vector_dimensions",
+        "type": "invalid_request",
+        "link": "https://docs.meilisearch.com/errors#invalid_vector_dimensions"
+      },
+      "duration": "[duration]",
+      "enqueuedAt": "[date]",
+      "startedAt": "[date]",
+      "finishedAt": "[date]"
+    }
+    "#);
+
+    // FIXME: /!\ Case where number of embeddings is divisor of `dimensions` would still pass
+    let new_document = json!([
+      {"id": 0, "name": "kefir", "_vectors": { "manual": [[0, 0], [1, 1], [2, 2]] }},
+    ]);
+    let (response, code) = index.add_documents(new_document, None).await;
+    snapshot!(code, @"202 Accepted");
+    index.wait_task(response.uid()).await.succeeded();
+    let (documents, _code) = index
+        .get_all_documents(GetAllDocumentsOptions { retrieve_vectors: true, ..Default::default() })
+        .await;
+    snapshot!(json_string!(documents), @r###"
+    {
+      "results": [
+        {
+          "id": 0,
+          "name": "kefir",
+          "_vectors": {
+            "manual": {
+              "embeddings": [
+                [
+                  0.0,
+                  0.0,
+                  1.0
+                ],
+                [
+                  1.0,
+                  2.0,
+                  2.0
+                ]
+              ],
+              "regenerate": false
+            }
+          }
+        }
+      ],
+      "offset": 0,
+      "limit": 20,
+      "total": 1
+    }
     "###);
 }
 
@@ -678,7 +769,7 @@ async fn add_remove_one_vector_4588() {
     let (documents, _code) = index
         .get_all_documents(GetAllDocumentsOptions { retrieve_vectors: true, ..Default::default() })
         .await;
-    snapshot!(json_string!(documents), @r###"
+    snapshot!(json_string!(documents), @r#"
     {
       "results": [
         {
@@ -696,5 +787,5 @@ async fn add_remove_one_vector_4588() {
       "limit": 20,
       "total": 1
     }
-    "###);
+    "#);
 }
diff --git a/crates/milli/src/update/new/indexer/write.rs b/crates/milli/src/update/new/indexer/write.rs
index 8618b4b21..ca860bbff 100644
--- a/crates/milli/src/update/new/indexer/write.rs
+++ b/crates/milli/src/update/new/indexer/write.rs
@@ -13,7 +13,7 @@ use crate::index::IndexEmbeddingConfig;
 use crate::progress::Progress;
 use crate::update::settings::InnerIndexSettings;
 use crate::vector::{ArroyWrapper, Embedder, EmbeddingConfigs, Embeddings};
-use crate::{Error, Index, InternalError, Result};
+use crate::{Error, Index, InternalError, Result, UserError};
 
 pub fn write_to_db(
     mut writer_receiver: WriterBbqueueReceiver<'_>,
@@ -218,7 +218,12 @@ pub fn write_from_bbqueue(
                     arroy_writers.get(&embedder_id).expect("requested a missing embedder");
                 let mut embeddings = Embeddings::new(*dimensions);
                 let all_embeddings = asvs.read_all_embeddings_into_vec(frame, aligned_embedding);
-                embeddings.append(all_embeddings.to_vec()).unwrap();
+                if embeddings.append(all_embeddings.to_vec()).is_err() {
+                    return Err(Error::UserError(UserError::InvalidVectorDimensions {
+                        expected: *dimensions,
+                        found: all_embeddings.len(),
+                    }));
+                }
                 writer.del_items(wtxn, *dimensions, docid)?;
                 writer.add_items(wtxn, docid, &embeddings)?;
             }