diff --git a/.github/workflows/linux.yml b/.github/workflows/linux.yml
index d241678a4131..eb580f6968c9 100644
--- a/.github/workflows/linux.yml
+++ b/.github/workflows/linux.yml
@@ -4,12 +4,12 @@ on: [push, pull_request]
 
 jobs:
   build:
-    runs-on: ubuntu-18.04
     strategy:
       matrix:
         cxx: [g++-4.8, g++-8, g++-10, clang++-9]
         build_type: [Debug, Release]
         std: [11]
+        os: [ubuntu-18.04]
         include:
           - cxx: g++-4.8
             install: sudo apt install g++-4.8
@@ -17,15 +17,20 @@ jobs:
             std: 14
           - cxx: g++-10
             std: 17
-          - cxx: g++-10
-            std: 20
-            cxxflags: -DFMT_COMPILE_TIME_CHECKS=1
+#          - cxx: g++-10
+#            std: 20
+#            cxxflags: -DFMT_COMPILE_TIME_CHECKS=1
+#            os: ubuntu-20.04
           - cxx: clang++-9
             std: 11
           - cxx: clang++-9
             build_type: Debug
             fuzz: -DFMT_FUZZ=ON -DFMT_FUZZ_LINKMAIN=ON
             std: 17
+#        exclude:
+#          - cxx: g++-10
+#            os: ubuntu-18.04
+    runs-on: ${{ matrix.os }}
 
     steps:
     - uses: actions/checkout@v2
diff --git a/include/fmt/format.h b/include/fmt/format.h
index 654540819ee6..5d90794c81d9 100644
--- a/include/fmt/format.h
+++ b/include/fmt/format.h
@@ -1674,7 +1674,7 @@ template <typename OutputIt, typename Char, typename UInt> struct int_writer {
     return string_view(prefix, prefix_size);
   }
 
-  void write_dec() {
+  constexpr void write_dec() {
     auto num_digits = count_digits(abs_value);
     out = write_int(
         out, num_digits, get_prefix(), specs, [this, num_digits](iterator it) {