diff --git a/rustfs/src/app/object_usecase.rs b/rustfs/src/app/object_usecase.rs
index dfb0485a0..0912d0127 100644
--- a/rustfs/src/app/object_usecase.rs
+++ b/rustfs/src/app/object_usecase.rs
@@ -312,6 +312,9 @@ impl DefaultObjectUsecase {
         let sse_customer_key = sse_customer_key.or(h_key);
         let sse_customer_key_md5 = sse_customer_key_md5.or(h_md5);
 
+        // Merge server_side_encryption from headers (fallback when S3 layer does not populate input)
+        let server_side_encryption = server_side_encryption.or(extract_server_side_encryption_from_headers(&req.headers)?);
+
         // Validate object key
         validate_object_key(&key, "PUT")?;
 
diff --git a/rustfs/src/storage/mod.rs b/rustfs/src/storage/mod.rs
index 63a45a007..49aab9913 100644
--- a/rustfs/src/storage/mod.rs
+++ b/rustfs/src/storage/mod.rs
@@ -35,7 +35,7 @@ mod sse_test;
 
 pub(crate) use ecfs_extend::*;
 pub(crate) use sse::{
-    DecryptionRequest, EncryptionRequest, PrepareEncryptionRequest, extract_ssec_params_from_headers, sse_decryption,
-    sse_encryption, sse_prepare_encryption, strip_managed_encryption_metadata, validate_sse_headers_for_read,
-    validate_sse_headers_for_write, validate_ssec_for_read,
+    DecryptionRequest, EncryptionRequest, PrepareEncryptionRequest, extract_server_side_encryption_from_headers,
+    extract_ssec_params_from_headers, sse_decryption, sse_encryption, sse_prepare_encryption, strip_managed_encryption_metadata,
+    validate_sse_headers_for_read, validate_sse_headers_for_write, validate_ssec_for_read,
 };
diff --git a/rustfs/src/storage/sse.rs b/rustfs/src/storage/sse.rs
index 83590cf80..679b2b4df 100644
--- a/rustfs/src/storage/sse.rs
+++ b/rustfs/src/storage/sse.rs
@@ -379,6 +379,21 @@ pub(crate) fn extract_ssec_params_from_headers(headers: &HeaderMap) -> Result<Ss
     Ok((algorithm, key, key_md5))
 }
 
+/// Extract x-amz-server-side-encryption from request headers.
+/// Used as fallback when the S3 layer does not populate it in the input struct.
+///
+/// Returns an error if the header is present but cannot be parsed as valid UTF-8,
+/// ensuring malformed headers do not bypass validation.
+pub(crate) fn extract_server_side_encryption_from_headers(headers: &HeaderMap) -> Result<Option<ServerSideEncryption>, ApiError> {
+    match headers.get("x-amz-server-side-encryption") {
+        None => Ok(None),
+        Some(v) => v
+            .to_str()
+            .map(|s| Some(ServerSideEncryption::from(s.to_string())))
+            .map_err(|_| sse_invalid_argument("The x-amz-server-side-encryption header must be valid UTF-8.")),
+    }
+}
+
 #[inline]
 pub(crate) fn validate_sse_headers_for_write(
     server_side_encryption: Option<&ServerSideEncryption>,
@@ -388,6 +403,15 @@ pub(crate) fn validate_sse_headers_for_write(
     sse_customer_key_md5: Option<&SSECustomerKeyMD5>,
     require_sse_customer_key: bool,
 ) -> Result<(), ApiError> {
+    if let Some(sse) = server_side_encryption {
+        let s = sse.as_str();
+        if s != ServerSideEncryption::AES256 && s != ServerSideEncryption::AWS_KMS {
+            return Err(sse_invalid_argument(
+                "The SSE algorithm specified is not supported. The valid values are AES256 or aws:kms.",
+            ));
+        }
+    }
+
     let has_ssec_headers = sse_customer_algorithm.is_some() || sse_customer_key.is_some() || sse_customer_key_md5.is_some();
     let has_managed_headers = server_side_encryption.is_some() || ssekms_key_id.is_some();
 
@@ -1752,6 +1776,17 @@ mod tests {
         assert_eq!(err.code, S3ErrorCode::InvalidArgument);
     }
 
+    #[test]
+    fn test_extract_server_side_encryption_from_headers_rejects_invalid_utf8() {
+        let mut headers = http::HeaderMap::new();
+        let invalid_utf8 = HeaderValue::from_bytes(b"aes:kms-\x80-invalid").unwrap();
+        headers.insert("x-amz-server-side-encryption", invalid_utf8);
+        let result = extract_server_side_encryption_from_headers(&headers);
+        assert!(result.is_err());
+        let err = result.unwrap_err();
+        assert_eq!(err.code, S3ErrorCode::InvalidArgument);
+    }
+
     #[test]
     fn test_validate_sse_headers_for_write_rejects_algorithm_without_key() {
         let algorithm = SSECustomerAlgorithm::from("AES256".to_string());
@@ -1785,6 +1820,15 @@ mod tests {
         assert_eq!(err.code, S3ErrorCode::InvalidRequest);
     }
 
+    #[test]
+    fn test_validate_sse_headers_for_write_rejects_invalid_sse_algorithm() {
+        let bad_sse = ServerSideEncryption::from_static("aes:kms");
+        let result = validate_sse_headers_for_write(Some(&bad_sse), None, None, None, None, true);
+        assert!(result.is_err());
+        let err = result.unwrap_err();
+        assert_eq!(err.code, S3ErrorCode::InvalidArgument);
+    }
+
     #[test]
     fn test_validate_sse_headers_for_write_rejects_ssec_with_managed_sse() {
         let algorithm = SSECustomerAlgorithm::from("AES256".to_string());
diff --git a/scripts/s3-tests/implemented_tests.txt b/scripts/s3-tests/implemented_tests.txt
index 7e147d0fd..4a921be23 100644
--- a/scripts/s3-tests/implemented_tests.txt
+++ b/scripts/s3-tests/implemented_tests.txt
@@ -20,7 +20,7 @@
 # - SSE-C: Server-side encryption with customer-provided keys
 # - Object ownership: Bucket ownership controls
 #
-# Total: 177 tests
+# Total: 182 tests
 
 test_basic_key_count
 test_bucket_create_naming_bad_short_one
@@ -162,7 +162,12 @@ test_encryption_sse_c_present
 test_encryption_sse_c_other_key
 test_encryption_sse_c_no_key
 test_encryption_sse_c_no_md5
+test_encryption_key_no_sse_c
+test_encryption_sse_c_invalid_md5
 test_put_obj_enc_conflict_c_s3
+test_put_obj_enc_conflict_c_kms
+test_put_obj_enc_conflict_s3_kms
+test_put_obj_enc_conflict_bad_enc_kms
 
 # ListObjectsV2 delimiter and encoding tests
 test_bucket_list_encoding_basic
diff --git a/scripts/s3-tests/unimplemented_tests.txt b/scripts/s3-tests/unimplemented_tests.txt
index 8982eba62..00cdd75a8 100644
--- a/scripts/s3-tests/unimplemented_tests.txt
+++ b/scripts/s3-tests/unimplemented_tests.txt
@@ -25,8 +25,6 @@ test_bucket_policy_put_obj_kms_s3
 test_bucket_policy_put_obj_s3_kms
 test_copy_enc
 test_copy_part_enc
-test_encryption_key_no_sse_c
-test_encryption_sse_c_invalid_md5
 test_encryption_sse_c_multipart_bad_download
 test_get_versioned_object_attributes
 test_lifecycle_delete
@@ -62,9 +60,6 @@ test_put_bucket_logging
 test_put_bucket_logging_errors
 test_put_bucket_logging_permissions
 test_put_bucket_logging_policy_wildcard
-test_put_obj_enc_conflict_bad_enc_kms
-test_put_obj_enc_conflict_c_kms
-test_put_obj_enc_conflict_s3_kms
 test_rm_bucket_logging
 test_sse_kms_no_key
 test_sse_kms_not_declared