diff --git a/include/internal/json_converter.hpp b/include/internal/json_converter.hpp
index 0b632269..e36a6a86 100644
--- a/include/internal/json_converter.hpp
+++ b/include/internal/json_converter.hpp
@@ -93,26 +93,65 @@ namespace csv {
             return out;
         }
 
-        inline void append_json_number_without_leading_zeros(
-            std::string& out,
-            csv::string_view value
-        ) noexcept {
+        CSV_CONST inline bool is_ascii_space(char c) noexcept {
+            return c == ' ' || (c >= '\t' && c <= '\r');
+        }
+
+        /** Append a numeric field as a JSON number.
+         *
+         *  data_type() accepts surrounding whitespace, a '+' sign, leading zeros,
+         *  and a '.' without a digit on one side, none of which JSON allows.
+         */
+        inline void append_json_number(std::string& out, csv::string_view value) noexcept {
             size_t first = 0;
-            if (first < value.size() && (value[first] == '+' || value[first] == '-')) {
+            size_t last = value.size();
+            while (first < last && is_ascii_space(value[first])) {
+                ++first;
+            }
+
+            while (last > first && is_ascii_space(value[last - 1])) {
+                --last;
+            }
+
+            if (first < last && (value[first] == '+' || value[first] == '-')) {
                 if (value[first] == '-') {
                     out += '-';
                 }
                 ++first;
             }
 
-            while (first + 1 < value.size()
+            while (first + 1 < last
                 && value[first] == '0'
                 && value[first + 1] >= '0'
                 && value[first + 1] <= '9') {
                 ++first;
             }
 
-            out.append(value.data() + first, value.size() - first);
+            if (first < last && value[first] == '.') {
+                out += '0';
+            }
+
+            for (size_t i = first; i < last; ++i) {
+                out += value[i];
+                if (value[i] == '.' && (i + 1 == last || value[i + 1] < '0' || value[i + 1] > '9')) {
+                    out += '0';
+                }
+            }
+        }
+
+        /** JSON has no hexadecimal literal, so write 0x-prefixed integers in decimal. */
+        inline bool append_json_hex_integer(std::string& out, csv::string_view value) {
+            if (value.find_first_of("xX") == csv::string_view::npos) {
+                return false;
+            }
+
+            long long parsed = 0;
+            if (!classify_scalar::parse_hex(value.data(), value.data() + value.size(), parsed)) {
+                return false;
+            }
+
+            out += std::to_string(parsed);
+            return true;
         }
 
         class JsonConverter {
@@ -235,7 +274,9 @@ namespace csv {
             void append_json_value(std::string& out, csv::string_view value) const {
                 const DataType type = internals::data_type(value);
                 if (type >= DataType::CSV_INT8 && type <= DataType::CSV_DOUBLE) {
-                    append_json_number_without_leading_zeros(out, value);
+                    if (type > DataType::CSV_INT64 || !append_json_hex_integer(out, value)) {
+                        append_json_number(out, value);
+                    }
                 } else if (type == DataType::CSV_NULL) {
                     out += "null";
                 } else {
diff --git a/tests/test_csv_row_json.cpp b/tests/test_csv_row_json.cpp
index e1ac8dc2..0fc3a479 100644
--- a/tests/test_csv_row_json.cpp
+++ b/tests/test_csv_row_json.cpp
@@ -118,6 +118,25 @@ TEST_CASE("CSVRow JSON serialization removes numeric leading zeros", "[csv_row_t
     REQUIRE(row.to_json_array() == "[69,-42,9,0,0.5,1e2]");
 }
 
+TEST_CASE("CSVRow JSON serialization writes valid numbers for every numeric field", "[csv_row_to_json]") {
+    CSVRow row = make_csv_row(
+        { ".5", "-.5", "+.5", "5.", "1.e5", " 08 ", " +2", "10.25" },
+        { "no_int", "neg_no_int", "pos_no_int", "no_frac", "no_frac_exp", "padded_zero", "padded_sign", "plain" }
+    );
+
+    REQUIRE(row.to_json_array() == "[0.5,-0.5,0.5,5.0,1.0e5,8,2,10.25]");
+}
+
+TEST_CASE("CSVRow JSON serialization writes hexadecimal integers in decimal", "[csv_row_to_json]") {
+    // Classification and hex conversion must agree on whitespace and a leading '+'.
+    CSVRow row = make_csv_row(
+        { "0x1F", "-0X10", "0x7FFFFFFFFFFFFFFF", "10", " \t+0X2A\r\n" },
+        { "hex", "neg_hex", "max_hex", "decimal", "padded_hex" }
+    );
+
+    REQUIRE(row.to_json_array() == "[31,-16,9223372036854775807,10,42]");
+}
+
 // Reported in: https://github.com/vincentlaucsb/csv-parser/issues/68
 TEST_CASE("CSVRow to_json() with Wrong Columns", "[csv_json_wrong_cols]") {
     std::stringstream csv_string(R"(A,B,C,