diff --git a/src/client/conn/http1.rs b/src/client/conn/http1.rs
index 2a9ca4f6e5..c2cc4d788b 100644
--- a/src/client/conn/http1.rs
+++ b/src/client/conn/http1.rs
@@ -387,6 +387,16 @@ impl Builder {
         self
     }
 
+    /// Set whether HTTP/1 connections will allow spaces before the first header,
+    /// which is not allowed by spec.
+    ///
+    /// Default is false.
+    pub fn allow_spaces_before_first_header_name(&mut self, enabled: bool) -> &mut Builder {
+        self.h1_parser_config
+            .allow_space_before_first_header_name(enabled);
+        self
+    }
+
     /// Set whether HTTP/1 connections should try to use vectored writes,
     /// or always flatten into a single buffer.
     ///
diff --git a/src/ffi/client.rs b/src/ffi/client.rs
index 975314b9be..8cf333d039 100644
--- a/src/ffi/client.rs
+++ b/src/ffi/client.rs
@@ -21,9 +21,11 @@ use super::task::{hyper_executor, hyper_task, hyper_task_return_type, AsTaskType
 /// - hyper_clientconn_options_set_preserve_header_case:  Set whether header case is preserved.
 /// - hyper_clientconn_options_set_preserve_header_order: Set whether header order is preserved.
 /// - hyper_clientconn_options_http1_allow_multiline_headers: Set whether HTTP/1 connections accept obsolete line folding for header values.
+/// - hyper_client_conn_options_http1_allow_spaces_before_first_header: Set whether HTTP/1 connections accept leading whitespaces before first header.
 /// - hyper_clientconn_options_free:    Free a set of HTTP clientconn options.
 pub struct hyper_clientconn_options {
     http1_allow_obsolete_multiline_headers_in_responses: bool,
+    http1_allow_spaces_before_first_header_name: bool,
     http1_preserve_header_case: bool,
     http1_preserve_header_order: bool,
     http2: bool,
@@ -116,6 +118,7 @@ ffi_fn! {
 
             conn::http1::Builder::new()
                 .allow_obsolete_multiline_headers_in_responses(options.http1_allow_obsolete_multiline_headers_in_responses)
+                .allow_spaces_before_first_header_name(options.http1_allow_spaces_before_first_header_name)
                 .preserve_header_case(options.http1_preserve_header_case)
                 .preserve_header_order(options.http1_preserve_header_order)
                 .handshake::<_, crate::body::Incoming>(io)
@@ -272,4 +275,17 @@ ffi_fn! {
         opts.http1_allow_obsolete_multiline_headers_in_responses = enabled != 0;
         hyper_code::HYPERE_OK
     }
+
+}
+
+ffi_fn! {
+    /// Set whether HTTP/1 connections accept leading whitespaces before first header.
+    ///
+    /// Pass `0` to disable, `1` to enable.
+    ///
+    fn hyper_clientconn_options_http1_allow_spaces_before_first_header_name(opts: *mut hyper_clientconn_options, enabled: c_int) -> hyper_code {
+        let opts = non_null! { &mut *opts ?= hyper_code::HYPERE_INVALID_ARG };
+        opts.http1_allow_spaces_before_first_header_name = enabled != 0;
+        hyper_code::HYPERE_OK
+    }
 }