diff --git a/MozillaFirefox.changes b/MozillaFirefox.changes
index 61b30c94..e49a4222 100644
--- a/MozillaFirefox.changes
+++ b/MozillaFirefox.changes
@@ -1,3 +1,8 @@
+-------------------------------------------------------------------
+Tue Dec  8 09:50:23 UTC 2020 - Martin Liška <mliska@suse.cz>
+
+- Add fix-gcc-pgo.patch and enable PGO again.
+
 -------------------------------------------------------------------
 Thu Dec  3 09:48:04 UTC 2020 - Martin Liška <mliska@suse.cz>
 
diff --git a/MozillaFirefox.spec b/MozillaFirefox.spec
index e2393301..076babb6 100644
--- a/MozillaFirefox.spec
+++ b/MozillaFirefox.spec
@@ -37,8 +37,7 @@
 %define branding       1
 %define devpkg         1
 
-# PGO builds do not work in TW currently (bmo#1642410)
-%define do_profiling   0
+%define do_profiling   1
 
 # upstream default is clang (to use gcc for large parts set to 0)
 %define clang_build 0
@@ -216,6 +215,7 @@ Patch29:        revert-795c8762b16b.patch
 # Firefox/browser
 Patch101:       firefox-kde.patch
 Patch102:       firefox-branded-icons.patch
+Patch103:       fix-gcc-pgo.patch
 %endif
 BuildRoot:      %{_tmppath}/%{name}-%{version}-build
 Requires(post):   coreutils shared-mime-info desktop-file-utils
@@ -358,6 +358,7 @@ cd $RPM_BUILD_DIR/%{srcname}-%{orig_version}
 # Firefox
 %patch101 -p1
 %patch102 -p1
+%patch103 -p1
 %endif
 
 %build
diff --git a/fix-gcc-pgo.patch b/fix-gcc-pgo.patch
new file mode 100644
index 00000000..ee179138
--- /dev/null
+++ b/fix-gcc-pgo.patch
@@ -0,0 +1,12 @@
+--- ./build/pgo/profileserver.py	2020-12-02 15:34:46.453053287 +0100
++++ ./build/pgo/profileserver.py	2020-12-02 15:34:57.988970433 +0100
+@@ -203,7 +203,8 @@
+             sys.exit(1)
+ 
+         llvm_profdata = env.get('LLVM_PROFDATA')
+-        if llvm_profdata:
++        cc = env.get('CC')
++        if llvm_profdata and not 'gcc' in cc:
+             profraw_files = glob.glob('*.profraw')
+             if not profraw_files:
+                 print('Could not find profraw files in the current directory: %s' % os.getcwd())