diff --git a/changelog/0.5.0.md b/changelog/0.5.0.md
index 56fbc71d..84f50a52 100644
--- a/changelog/0.5.0.md
+++ b/changelog/0.5.0.md
@@ -69,7 +69,6 @@
     :barbar: b    # was ok
     :barbarbar: c # was ol
   ```
-- Fix [#246](https://github.com/biojppm/rapidyaml/issues/246): add missing `#define` for the include guard of the amalgamated header.
 - Fix [#253](https://github.com/biojppm/rapidyaml/issues/253): double-quoted emitter should encode carriage-return `\r` to preserve roundtrip equivalence:
   ```yaml
   Tree tree;
@@ -83,6 +82,8 @@
   EXPECT_EQ(tree2["s"].val(), tree["s"].val());
   ```
 - Fix [#297](https://github.com/biojppm/rapidyaml/issues/297) ([PR#298](https://github.com/biojppm/rapidyaml/pull/298)): JSON emitter should escape control characters.
+- Fix [#292](https://github.com/biojppm/rapidyaml/issues/292) ([PR#299](https://github.com/biojppm/rapidyaml/pull/299)): JSON emitter should quote version string scalars like `0.1.2`.
+- Fix [#291](https://github.com/biojppm/rapidyaml/issues/291) ([PR#299](https://github.com/biojppm/rapidyaml/pull/299)): JSON emitter should quote scalars with leading zero, eg `048`.
 - Fix [#274](https://github.com/biojppm/rapidyaml/issues/274) ([PR#296](https://github.com/biojppm/rapidyaml/pull/296)): Lists with unindented items and trailing empty values parse incorrectly:
   ```yaml
   foo:
@@ -106,4 +107,5 @@
   =VAL :foo
   =VAL :bar
   ```
+- Fix [#246](https://github.com/biojppm/rapidyaml/issues/246): add missing `#define` for the include guard of the amalgamated header.
 - Fix [cmake#8](https://github.com/biojppm/cmake/issues/8): `SOVERSION` missing from shared libraries.
diff --git a/ext/c4core b/ext/c4core
index 3729e3fd..cad3d1f1 160000
--- a/ext/c4core
+++ b/ext/c4core
@@ -1 +1 @@
-Subproject commit 3729e3fdfa5df6072e1b2d0dcea755d7e977ad58
+Subproject commit cad3d1f1b385561b9974d1df0032c97bf880f5a1
diff --git a/samples/quickstart.cpp b/samples/quickstart.cpp
index 511f4af7..8b5f1f05 100644
--- a/samples/quickstart.cpp
+++ b/samples/quickstart.cpp
@@ -1211,23 +1211,35 @@ void sample_substr()
         CHECK(ryml::csubstr("-1234)asdkjh").first_real_span() == "-1234");
         CHECK(ryml::csubstr("-1234gasdkjh").first_real_span() == "");
         CHECK(ryml::csubstr("1.234 asdkjh").first_real_span() == "1.234");
-        CHECK(ryml::csubstr("1.234e5 asdkjh").first_real_span() == "1.234e5");
         CHECK(ryml::csubstr("1.234e+5 asdkjh").first_real_span() == "1.234e+5");
         CHECK(ryml::csubstr("1.234e-5 asdkjh").first_real_span() == "1.234e-5");
         CHECK(ryml::csubstr("1.234 asdkjh").first_real_span() == "1.234");
-        CHECK(ryml::csubstr("1.234e5 asdkjh").first_real_span() == "1.234e5");
         CHECK(ryml::csubstr("1.234e+5 asdkjh").first_real_span() == "1.234e+5");
         CHECK(ryml::csubstr("1.234e-5 asdkjh").first_real_span() == "1.234e-5");
         CHECK(ryml::csubstr("-1.234 asdkjh").first_real_span() == "-1.234");
-        CHECK(ryml::csubstr("-1.234e5 asdkjh").first_real_span() == "-1.234e5");
         CHECK(ryml::csubstr("-1.234e+5 asdkjh").first_real_span() == "-1.234e+5");
         CHECK(ryml::csubstr("-1.234e-5 asdkjh").first_real_span() == "-1.234e-5");
+        // hexadecimal real numbers
         CHECK(ryml::csubstr("0x1.e8480p+19 asdkjh").first_real_span() == "0x1.e8480p+19");
         CHECK(ryml::csubstr("0x1.e8480p-19 asdkjh").first_real_span() == "0x1.e8480p-19");
         CHECK(ryml::csubstr("-0x1.e8480p+19 asdkjh").first_real_span() == "-0x1.e8480p+19");
         CHECK(ryml::csubstr("-0x1.e8480p-19 asdkjh").first_real_span() == "-0x1.e8480p-19");
         CHECK(ryml::csubstr("+0x1.e8480p+19 asdkjh").first_real_span() == "+0x1.e8480p+19");
         CHECK(ryml::csubstr("+0x1.e8480p-19 asdkjh").first_real_span() == "+0x1.e8480p-19");
+        // binary real numbers
+        CHECK(ryml::csubstr("0b101.011p+19 asdkjh").first_real_span() == "0b101.011p+19");
+        CHECK(ryml::csubstr("0b101.011p-19 asdkjh").first_real_span() == "0b101.011p-19");
+        CHECK(ryml::csubstr("-0b101.011p+19 asdkjh").first_real_span() == "-0b101.011p+19");
+        CHECK(ryml::csubstr("-0b101.011p-19 asdkjh").first_real_span() == "-0b101.011p-19");
+        CHECK(ryml::csubstr("+0b101.011p+19 asdkjh").first_real_span() == "+0b101.011p+19");
+        CHECK(ryml::csubstr("+0b101.011p-19 asdkjh").first_real_span() == "+0b101.011p-19");
+        // octal real numbers
+        CHECK(ryml::csubstr("0o173.045p+19 asdkjh").first_real_span() == "0o173.045p+19");
+        CHECK(ryml::csubstr("0o173.045p-19 asdkjh").first_real_span() == "0o173.045p-19");
+        CHECK(ryml::csubstr("-0o173.045p+19 asdkjh").first_real_span() == "-0o173.045p+19");
+        CHECK(ryml::csubstr("-0o173.045p-19 asdkjh").first_real_span() == "-0o173.045p-19");
+        CHECK(ryml::csubstr("+0o173.045p+19 asdkjh").first_real_span() == "+0o173.045p+19");
+        CHECK(ryml::csubstr("+0o173.045p-19 asdkjh").first_real_span() == "+0o173.045p-19");
     }
     // see also is_number()
 
diff --git a/src/c4/yml/emit.def.hpp b/src/c4/yml/emit.def.hpp
index 653714e0..4aa03c11 100644
--- a/src/c4/yml/emit.def.hpp
+++ b/src/c4/yml/emit.def.hpp
@@ -879,7 +879,10 @@ template<class Writer>
 void Emitter<Writer>::_write_scalar_json(csubstr s, bool as_key, bool was_quoted)
 {
     // json only allows strings as keys
-    if(!as_key && !was_quoted && (s.is_number() || s == "true" || s == "null" || s == "false"))
+    if((!as_key)
+       && (!was_quoted)
+       && ((s.is_number() && !(s.len > 1 && s.str[0] == '0'))
+           || s == "true" || s == "null" || s == "false"))
     {
         this->Writer::_do_write(s);
     }
diff --git a/test/test_json.cpp b/test/test_json.cpp
index fb88f06e..d836e517 100644
--- a/test/test_json.cpp
+++ b/test/test_json.cpp
@@ -220,6 +220,23 @@ broken_value: '0.30.2'
 )");
 }
 
+TEST(emit_json, issue291)
+{
+    Tree t = parse_in_arena("{}");
+    t["james"] = "045";
+    auto s = emitrs_json<std::string>(t);
+    EXPECT_EQ(s, "{\"james\": \"045\"}");
+}
+
+TEST(emit_json, issue292)
+{
+    EXPECT_FALSE(csubstr("0.1.0").is_number());
+    Tree t = parse_in_arena("{}");
+    t["james"] = "1.2.3";
+    auto s = emitrs_json<std::string>(t);
+    EXPECT_EQ(s, "{\"james\": \"1.2.3\"}");
+}
+
 TEST(emit_json, issue297)
 {
     char yml_buf[] = R"(