diff --git a/src/db/options.rs b/src/db/options.rs
index ee987ce28..03848e841 100644
--- a/src/db/options.rs
+++ b/src/db/options.rs
@@ -44,7 +44,11 @@ pub struct CreateCollectionOptions {
 
     /// The maximum size (in bytes) for a capped collection. This option is ignored if `capped` is
     /// not set to true.
-    #[serde(serialize_with = "serde_util::serialize_u64_option_as_i64")]
+    #[serde(
+        serialize_with = "serde_util::serialize_u64_option_as_i64",
+        deserialize_with = "serde_util::deserialize_option_u64_from_bson_number",
+        default
+    )]
     pub size: Option<u64>,
 
     /// The maximum number of documents in a capped collection. The `size` limit takes precedence
diff --git a/src/serde_util.rs b/src/serde_util.rs
index d3dcda433..b8046bd37 100644
--- a/src/serde_util.rs
+++ b/src/serde_util.rs
@@ -118,6 +118,21 @@ where
         .ok_or_else(|| serde::de::Error::custom(format!("could not deserialize u64 from {bson:?}")))
 }
 
+pub(crate) fn deserialize_option_u64_from_bson_number<'de, D>(
+    deserializer: D,
+) -> std::result::Result<Option<u64>, D::Error>
+where
+    D: Deserializer<'de>,
+{
+    Option::<Bson>::deserialize(deserializer)?
+        .map(|bson| {
+            get_u64(&bson).ok_or_else(|| {
+                serde::de::Error::custom(format!("could not deserialize u64 from {bson:?}"))
+            })
+        })
+        .transpose()
+}
+
 pub(crate) fn serialize_error_as_string<S: Serializer>(
     val: &Error,
     serializer: S,
diff --git a/src/test/db.rs b/src/test/db.rs
index b13df1abc..3b4a25213 100644
--- a/src/test/db.rs
+++ b/src/test/db.rs
@@ -468,3 +468,18 @@ async fn test_run_command() {
         assert_eq!(v[0].as_ref().unwrap().get_str("foo").unwrap(), "bar");
     }
 }
+
+#[test]
+fn create_collection_options_deserialize() {
+    let source = doc! {
+        "capped": true,
+        "size": 5253511168.0,
+        "autoIndexId": false,
+    };
+    let _: CreateCollectionOptions = crate::bson_compat::deserialize_from_document(source).unwrap();
+    let source = doc! {
+        "capped": true,
+        "autoIndexId": false,
+    };
+    let _: CreateCollectionOptions = crate::bson_compat::deserialize_from_document(source).unwrap();
+}