diff --git a/datafusion-postgres/src/handlers.rs b/datafusion-postgres/src/handlers.rs
index 1110a0b..6067e37 100644
--- a/datafusion-postgres/src/handlers.rs
+++ b/datafusion-postgres/src/handlers.rs
@@ -1,3 +1,4 @@
+use std::collections::HashMap;
 use std::sync::Arc;
 
 use async_trait::async_trait;
@@ -138,9 +139,9 @@ impl ExtendedQueryHandler for DfSessionService {
             .map_err(|e| PgWireError::ApiError(Box::new(e)))?;
 
         let mut param_types = Vec::with_capacity(params.len());
-        for param_type in params.into_values() {
+        for param_type in ordered_param_types(&params).iter() {
             if let Some(datatype) = param_type {
-                let pgtype = into_pg_type(&datatype)?;
+                let pgtype = into_pg_type(datatype)?;
                 param_types.push(pgtype);
             } else {
                 param_types.push(Type::UNKNOWN);
@@ -177,15 +178,12 @@ impl ExtendedQueryHandler for DfSessionService {
     {
         let plan = &portal.statement.statement;
 
-        let param_values = datatypes::deserialize_parameters(
-            portal,
-            &plan
-                .get_parameter_types()
-                .map_err(|e| PgWireError::ApiError(Box::new(e)))?
-                .values()
-                .map(|v| v.as_ref())
-                .collect::<Vec<Option<&DataType>>>(),
-        )?;
+        let param_types = plan
+            .get_parameter_types()
+            .map_err(|e| PgWireError::ApiError(Box::new(e)))?;
+
+        let param_values =
+            datatypes::deserialize_parameters(portal, &ordered_param_types(&param_types))?;
 
         let plan = plan
             .clone()
@@ -202,3 +200,12 @@ impl ExtendedQueryHandler for DfSessionService {
         Ok(Response::Query(resp))
     }
 }
+
+fn ordered_param_types(types: &HashMap<String, Option<DataType>>) -> Vec<Option<&DataType>> {
+    // Datafusion stores the parameters as a map.  In our case, the keys will be
+    // `$1`, `$2` etc.  The values will be the parameter types.
+
+    let mut types = types.iter().collect::<Vec<_>>();
+    types.sort_by(|a, b| a.0.cmp(b.0));
+    types.into_iter().map(|pt| pt.1.as_ref()).collect()
+}