diff --git a/src/shrpx_http.cc b/src/shrpx_http.cc
index 8ac787a0..32d508f0 100644
--- a/src/shrpx_http.cc
+++ b/src/shrpx_http.cc
@@ -122,6 +122,15 @@ void capitalize(std::string& s, size_t offset)
   }
 }
 
+void sanitize_header_value(std::string& s, size_t offset)
+{
+  for(size_t i = offset, eoi = s.size(); i < eoi; ++i) {
+    if(s[i] == '\r' || s[i] == '\n') {
+      s[i] = ' ';
+    }
+  }
+}
+
 std::string colorizeHeaders(const char *hdrs)
 {
   std::string nhdrs;
diff --git a/src/shrpx_http.h b/src/shrpx_http.h
index 61b05235..e5732c70 100644
--- a/src/shrpx_http.h
+++ b/src/shrpx_http.h
@@ -41,6 +41,8 @@ std::string create_via_header_value(int major, int minor);
 
 void capitalize(std::string& s, size_t offset);
 
+void sanitize_header_value(std::string& s, size_t offset);
+
 // Adds ANSI color codes to HTTP headers |hdrs|.
 std::string colorizeHeaders(const char *hdrs);
 
diff --git a/src/shrpx_http_downstream_connection.cc b/src/shrpx_http_downstream_connection.cc
index 4e7413c2..68fcc9c3 100644
--- a/src/shrpx_http_downstream_connection.cc
+++ b/src/shrpx_http_downstream_connection.cc
@@ -160,6 +160,7 @@ int HttpDownstreamConnection::push_request_headers()
     http::capitalize(hdrs, hdrs.size()-(*i).first.size());
     hdrs += ": ";
     hdrs += (*i).second;
+    http::sanitize_header_value(hdrs, hdrs.size()-(*i).second.size());
     hdrs += "\r\n";
   }
   if(downstream_->get_request_connection_close()) {