diff --git a/header.go b/header.go
index b3434c3556..99e1dcc42d 100644
--- a/header.go
+++ b/header.go
@@ -681,8 +681,6 @@ func (h *RequestHeader) RequestURI() []byte {
 	requestURI := h.requestURI
 	if len(requestURI) == 0 {
 		requestURI = strSlash
-	} else if requestURI[0] == '?' {
-		requestURI = append(strSlash, requestURI...)
 	}
 	return requestURI
 }
@@ -691,6 +689,11 @@ func (h *RequestHeader) RequestURI() []byte {
 // RequestURI must be properly encoded.
 // Use URI.RequestURI for constructing proper RequestURI if unsure.
 func (h *RequestHeader) SetRequestURI(requestURI string) {
+	if len(requestURI) > 0 && requestURI[0] == '?' {
+		h.requestURI = append(h.requestURI[:0], strSlash...)
+		h.requestURI = append(h.requestURI, requestURI...)
+		return
+	}
 	h.requestURI = append(h.requestURI[:0], requestURI...)
 }
 
@@ -698,6 +701,11 @@ func (h *RequestHeader) SetRequestURI(requestURI string) {
 // RequestURI must be properly encoded.
 // Use URI.RequestURI for constructing proper RequestURI if unsure.
 func (h *RequestHeader) SetRequestURIBytes(requestURI []byte) {
+	if len(requestURI) > 0 && requestURI[0] == '?' {
+		h.requestURI = append(h.requestURI[:0], strSlash...)
+		h.requestURI = append(h.requestURI, requestURI...)
+		return
+	}
 	h.requestURI = append(h.requestURI[:0], requestURI...)
 }
 
diff --git a/header_test.go b/header_test.go
index 8d4f7cdb70..0c7fdc1cab 100644
--- a/header_test.go
+++ b/header_test.go
@@ -1261,6 +1261,26 @@ func TestRequestHeaderWithQueryParamsAndNoPath(t *testing.T) {
 	if w.String() != expectedRequestHeader {
 		t.Fatalf("unexpected request header: %q. Expecting %q", w, expectedRequestHeader)
 	}
+
+	h1.Reset()
+	h1.SetRequestURIBytes([]byte("?foo=bar"))
+	h1.SetHost("example.com")
+	h1.SetMethod("GET")
+
+	w.Reset()
+	bw = bufio.NewWriter(w)
+	if err := h1.Write(bw); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if err := bw.Flush(); err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+
+	expectedRequestHeader = "GET /?foo=bar HTTP/1.1\r\nHost: example.com\r\n\r\n"
+	if w.String() != expectedRequestHeader {
+		t.Fatalf("unexpected request header: %q. Expecting %q", w, expectedRequestHeader)
+	}
+
 }
 
 func TestResponseHeaderFirstByteReadEOF(t *testing.T) {