diff --git a/src/json.hpp b/src/json.hpp
index 66756d90..b3613ea3 100644
--- a/src/json.hpp
+++ b/src/json.hpp
@@ -1853,7 +1853,8 @@ class basic_json
     recursively. Note that
 
     - strings and object keys are escaped using escape_string()
-    - numbers are converted to a string before output using std::to_string()
+    - integer numbers are converted to a string before output using std::to_string()
+    - floating-point numbers are converted to a string using "%g" format
 
     @param prettyPrint    whether the output shall be pretty-printed
     @param indentStep     the indent level
@@ -1961,7 +1962,12 @@ class basic_json
 
             case (value_t::number_float):
             {
-                return std::to_string(m_value.number_float);
+                // 15 digits of precision allows round-trip IEEE 754 string->double->string
+                unsigned int sz = (unsigned int)std::snprintf(nullptr, 0, "%.15g", m_value.number_float);
+                std::vector<char> buf(sz + 1);
+                std::snprintf(&buf[0], buf.size(), "%.15g", m_value.number_float);
+                string_t formatted = buf.data();
+                return formatted;
             }
 
             default: