diff --git a/qt5-qtwebkit.spec b/qt5-qtwebkit.spec
index 64f4fb2..9f53405 100644
--- a/qt5-qtwebkit.spec
+++ b/qt5-qtwebkit.spec
@@ -26,6 +26,7 @@ Source0:        https://github.com/qtwebkit/qtwebkit/releases/download/%{qt_modu
 # Patch for new CMake policy CMP0071 to explicitly use old behaviour.
 Patch2:         qtwebkit-5.212.0_cmake_cmp0071.patch
 Patch3:         qtwebkit-5.212.0-json.patch
+Patch4:         qtwebkit-bison37.patch
 
 BuildRequires:  bison
 BuildRequires:  cmake
diff --git a/qtwebkit-bison37.patch b/qtwebkit-bison37.patch
new file mode 100644
index 0000000..488dfda
--- /dev/null
+++ b/qtwebkit-bison37.patch
@@ -0,0 +1,39 @@
+Description: let Bison generate the header directly
+ Starting with Bison 3.7, the generated C++ file #include's the header
+ by default, instead of duplicating it. So we should not delete it.
+ .
+ Remove the code to add #ifdef guards to the header, since Bison adds
+ them itself since version 2.6.3.
+Author: Dmitry Shachnev <mitya57@debian.org>
+Forwarded: not-yet
+Last-Update: 2020-08-04
+
+--- a/Source/WebCore/css/makegrammar.pl
++++ b/Source/WebCore/css/makegrammar.pl
+@@ -73,25 +73,6 @@ if ($suffix eq ".y.in") {
+ }
+ 
+ my $fileBase = File::Spec->join($outputDir, $filename);
+-my @bisonCommand = ($bison, "-d", "-p", $symbolsPrefix, $grammarFilePath, "-o", "$fileBase.cpp");
++my @bisonCommand = ($bison, "--defines=$fileBase.h", "-p", $symbolsPrefix, $grammarFilePath, "-o", "$fileBase.cpp");
+ push @bisonCommand, "--no-lines" if $^O eq "MSWin32"; # Work around bug in bison >= 3.0 on Windows where it puts backslashes into #line directives.
+ system(@bisonCommand) == 0 or die;
+-
+-open HEADER, ">$fileBase.h" or die;
+-print HEADER << "EOF";
+-#ifndef CSSGRAMMAR_H
+-#define CSSGRAMMAR_H
+-EOF
+-
+-open HPP, "<$fileBase.cpp.h" or open HPP, "<$fileBase.hpp" or die;
+-while (<HPP>) {
+-    print HEADER;
+-}
+-close HPP;
+-
+-print HEADER "#endif\n";
+-close HEADER;
+-
+-unlink("$fileBase.cpp.h");
+-unlink("$fileBase.hpp");
+-