diff --git a/Cargo.lock b/Cargo.lock
index 1508f4a8..95eb9480 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -125,9 +125,9 @@ dependencies = [
 
 [[package]]
 name = "async-trait"
-version = "0.1.27"
+version = "0.1.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "991d0a1a3e790c835fd54ab41742a59251338d8c7577fe7d7f0170c7072be708"
+checksum = "da71fef07bc806586090247e971229289f64c210a278ee5ae419314eb386b31d"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -303,6 +303,7 @@ name = "cargo-sqlx"
 version = "0.1.0"
 dependencies = [
  "anyhow",
+ "async-trait",
  "chrono",
  "dotenv",
  "futures 0.3.4",
diff --git a/sqlx-core/src/mysql/types/json.rs b/sqlx-core/src/mysql/types/json.rs
index d62c3148..5be6d68c 100644
--- a/sqlx-core/src/mysql/types/json.rs
+++ b/sqlx-core/src/mysql/types/json.rs
@@ -14,18 +14,6 @@ impl Type<MySql> for JsonValue {
     }
 }
 
-impl Encode<MySql> for JsonValue {
-    fn encode(&self, buf: &mut Vec<u8>) {
-        (Box::new(Json(self)) as Box<dyn Encode<MySql>>).encode(buf)
-    }
-}
-
-impl<'de> Decode<'de, MySql> for JsonValue {
-    fn decode(value: MySqlValue<'de>) -> crate::Result<Self> {
-        <Json<Self> as Decode<MySql>>::decode(value).map(|item| item.0)
-    }
-}
-
 impl<T> Type<MySql> for Json<T> {
     fn type_info() -> MySqlTypeInfo {
         // MySql uses the CHAR type to pass JSON data from and to the client
diff --git a/sqlx-core/src/postgres/types/json.rs b/sqlx-core/src/postgres/types/json.rs
index ef2b82b0..20aeedcd 100644
--- a/sqlx-core/src/postgres/types/json.rs
+++ b/sqlx-core/src/postgres/types/json.rs
@@ -21,36 +21,12 @@ impl Type<Postgres> for JsonValue {
     }
 }
 
-impl Encode<Postgres> for JsonValue {
-    fn encode(&self, buf: &mut PgRawBuffer) {
-        (Box::new(Json(self)) as Box<dyn Encode<Postgres>>).encode(buf)
-    }
-}
-
-impl<'de> Decode<'de, Postgres> for JsonValue {
-    fn decode(value: PgValue<'de>) -> crate::Result<Self> {
-        <Json<Self> as Decode<Postgres>>::decode(value).map(|item| item.0)
-    }
-}
-
 impl Type<Postgres> for &'_ JsonRawValue {
     fn type_info() -> PgTypeInfo {
         <Json<Self> as Type<Postgres>>::type_info()
     }
 }
 
-impl Encode<Postgres> for &'_ JsonRawValue {
-    fn encode(&self, buf: &mut PgRawBuffer) {
-        (Box::new(Json(self)) as Box<dyn Encode<Postgres>>).encode(buf)
-    }
-}
-
-impl<'de> Decode<'de, Postgres> for &'de JsonRawValue {
-    fn decode(value: PgValue<'de>) -> crate::Result<Self> {
-        <Json<Self> as Decode<Postgres>>::decode(value).map(|item| item.0)
-    }
-}
-
 impl<T> Type<Postgres> for Json<T> {
     fn type_info() -> PgTypeInfo {
         PgTypeInfo::new(TypeId::JSONB, "JSONB")
diff --git a/sqlx-core/src/types.rs b/sqlx-core/src/types.rs
index 7bae04ba..fa817861 100644
--- a/sqlx-core/src/types.rs
+++ b/sqlx-core/src/types.rs
@@ -43,6 +43,12 @@ pub mod ipnetwork {
 
 #[cfg(feature = "json")]
 pub mod json {
+    use crate::database::Database;
+    use crate::decode::Decode;
+    use crate::encode::Encode;
+    use crate::value::HasRawValue;
+    use serde_json::value::RawValue as JsonRawValue;
+    use serde_json::Value as JsonValue;
     use std::ops::Deref;
 
     #[cfg_attr(docsrs, doc(cfg(feature = "json")))]
@@ -62,6 +68,38 @@ pub mod json {
             &self.0
         }
     }
+
+    impl<DB> Encode<DB> for JsonValue
+    where
+        Json<Self>: Encode<DB>,
+        DB: Database,
+    {
+        fn encode(&self, buf: &mut DB::RawBuffer) {
+            <Json<Self> as Encode<DB>>::encode(&Json(self.clone()), buf)
+        }
+    }
+
+    impl<'de, DB> Decode<'de, DB> for JsonValue
+    where
+        Json<Self>: Decode<'de, DB>,
+        DB: Database,
+    {
+        fn decode(value: <DB as HasRawValue<'de>>::RawValue) -> crate::Result<Self> {
+            <Json<Self> as Decode<DB>>::decode(value).map(|item| item.0)
+        }
+    }
+
+    // We don't have to implement Encode for JsonRawValue because that's covered by the default
+    // implementation for Encode
+    impl<'de, DB> Decode<'de, DB> for &'de JsonRawValue
+    where
+        Json<Self>: Decode<'de, DB>,
+        DB: Database,
+    {
+        fn decode(value: <DB as HasRawValue<'de>>::RawValue) -> crate::Result<Self> {
+            <Json<Self> as Decode<DB>>::decode(value).map(|item| item.0)
+        }
+    }
 }
 #[cfg(feature = "json")]
 pub use self::json::Json;