diff --git a/src/json.hpp b/src/json.hpp
index 14780ca8c..e0d94f776 100644
--- a/src/json.hpp
+++ b/src/json.hpp
@@ -6429,7 +6429,7 @@ class basic_json
 
             while(x and i < s_capacity) 
             {
-                m_buf[i++] = '0' + abs(x % 10);
+                m_buf[i++] = static_cast<char>('0' + std::labs(x % 10));
                 x /= 10;
             }
 
diff --git a/src/json.hpp.re2c b/src/json.hpp.re2c
index cac41603e..87977da66 100644
--- a/src/json.hpp.re2c
+++ b/src/json.hpp.re2c
@@ -6429,7 +6429,7 @@ class basic_json
 
             while(x and i < s_capacity) 
             {
-                m_buf[i++] = '0' + abs(x % 10);
+                m_buf[i++] = static_cast<char>('0' + std::labs(x % 10));
                 x /= 10;
             }