diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 5541a357..8d2140c9 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -23,6 +23,10 @@ jobs:
             cc: clang
             cxx: clang++
             type: shared
+          - os: macos-latest
+            cc: gcc-13
+            cxx: g++-13
+            type: static
           - os: ubuntu-latest
             cc: clang
             cxx: clang++
diff --git a/Brewfile b/Brewfile
index a42e1111..bfe8ba28 100644
--- a/Brewfile
+++ b/Brewfile
@@ -1,2 +1,3 @@
 brew "cmake"
 brew "sassc"
+brew "gcc@13"
diff --git a/src/runtime/include/sourcemeta/jsonbinpack/runtime_decoder.h b/src/runtime/include/sourcemeta/jsonbinpack/runtime_decoder.h
index 8d01b6a9..f03372ef 100644
--- a/src/runtime/include/sourcemeta/jsonbinpack/runtime_decoder.h
+++ b/src/runtime/include/sourcemeta/jsonbinpack/runtime_decoder.h
@@ -209,9 +209,9 @@ class Decoder : private BasicDecoder<CharT, Traits> {
     if (is_shared) {
       const std::uint64_t position{this->position()};
       const std::uint64_t current{this->rewind(this->get_varint(), position)};
-      sourcemeta::jsontoolkit::JSON string{this->get_string_utf8(length)};
+      const sourcemeta::jsontoolkit::JSON value{this->get_string_utf8(length)};
       this->seek(current);
-      return string;
+      return value;
     } else {
       return UTF8_STRING_NO_LENGTH({length});
     }
@@ -229,9 +229,10 @@ class Decoder : private BasicDecoder<CharT, Traits> {
     if (is_shared) {
       const std::uint64_t position{this->position()};
       const std::uint64_t current{this->rewind(this->get_varint(), position)};
-      sourcemeta::jsontoolkit::JSON string = UTF8_STRING_NO_LENGTH({length});
+      const sourcemeta::jsontoolkit::JSON value{
+          UTF8_STRING_NO_LENGTH({length})};
       this->seek(current);
-      return string;
+      return value;
     } else {
       return UTF8_STRING_NO_LENGTH({length});
     }
@@ -251,9 +252,10 @@ class Decoder : private BasicDecoder<CharT, Traits> {
     if (is_shared) {
       const std::uint64_t position{this->position()};
       const std::uint64_t current{this->rewind(this->get_varint(), position)};
-      sourcemeta::jsontoolkit::JSON string = UTF8_STRING_NO_LENGTH({length});
+      const sourcemeta::jsontoolkit::JSON value{
+          UTF8_STRING_NO_LENGTH({length})};
       this->seek(current);
-      return string;
+      return value;
     } else {
       return UTF8_STRING_NO_LENGTH({length});
     }
@@ -289,10 +291,10 @@ class Decoder : private BasicDecoder<CharT, Traits> {
     if (prefix == 0) {
       const std::uint64_t position{this->position()};
       const std::uint64_t current{this->rewind(this->get_varint(), position)};
-      sourcemeta::jsontoolkit::JSON string =
-          PREFIX_VARINT_LENGTH_STRING_SHARED(options);
+      const sourcemeta::jsontoolkit::JSON value{
+          PREFIX_VARINT_LENGTH_STRING_SHARED(options)};
       this->seek(current);
-      return string;
+      return value;
     } else {
       return sourcemeta::jsontoolkit::JSON{this->get_string_utf8(prefix - 1)};
     }
@@ -438,9 +440,10 @@ class Decoder : private BasicDecoder<CharT, Traits> {
           const std::uint64_t position{this->position()};
           const std::uint64_t current{
               this->rewind(this->get_varint(), position)};
-          sourcemeta::jsontoolkit::JSON string{this->get_string_utf8(length)};
+          const sourcemeta::jsontoolkit::JSON value{
+              this->get_string_utf8(length)};
           this->seek(current);
-          return string;
+          return value;
         };
         case TYPE_STRING:
           return subtype == 0 ? this->FLOOR_VARINT_PREFIX_UTF8_STRING_SHARED(