diff --git a/src/json.hpp b/src/json.hpp
index 6e49b4d9..5ad77f9d 100644
--- a/src/json.hpp
+++ b/src/json.hpp
@@ -7046,7 +7046,7 @@ class basic_json
                 const auto N = j.m_value.string->size();
                 if (N <= 0x17)
                 {
-                    v.push_back(0x60 + N);  // 1 byte for string + size
+                    v.push_back(0x60 + static_cast<uint8_t>(N));  // 1 byte for string + size
                 }
                 else if (N <= 0xff)
                 {
@@ -7082,7 +7082,7 @@ class basic_json
                 const auto N = j.m_value.array->size();
                 if (N <= 0x17)
                 {
-                    v.push_back(0x80 + N);  // 1 byte for array + size
+                    v.push_back(0x80 + static_cast<uint8_t>(N));  // 1 byte for array + size
                 }
                 else if (N <= 0xff)
                 {
@@ -7120,7 +7120,7 @@ class basic_json
                 const auto N = j.m_value.object->size();
                 if (N <= 0x17)
                 {
-                    v.push_back(0xa0 + N);  // 1 byte for object + size
+                    v.push_back(0xa0 + static_cast<uint8_t>(N));  // 1 byte for object + size
                 }
                 else if (N <= 0xff)
                 {
diff --git a/src/json.hpp.re2c b/src/json.hpp.re2c
index dae2e958..84c0e893 100644
--- a/src/json.hpp.re2c
+++ b/src/json.hpp.re2c
@@ -7046,7 +7046,7 @@ class basic_json
                 const auto N = j.m_value.string->size();
                 if (N <= 0x17)
                 {
-                    v.push_back(0x60 + N);  // 1 byte for string + size
+                    v.push_back(0x60 + static_cast<uint8_t>(N));  // 1 byte for string + size
                 }
                 else if (N <= 0xff)
                 {
@@ -7082,7 +7082,7 @@ class basic_json
                 const auto N = j.m_value.array->size();
                 if (N <= 0x17)
                 {
-                    v.push_back(0x80 + N);  // 1 byte for array + size
+                    v.push_back(0x80 + static_cast<uint8_t>(N));  // 1 byte for array + size
                 }
                 else if (N <= 0xff)
                 {
@@ -7120,7 +7120,7 @@ class basic_json
                 const auto N = j.m_value.object->size();
                 if (N <= 0x17)
                 {
-                    v.push_back(0xa0 + N);  // 1 byte for object + size
+                    v.push_back(0xa0 + static_cast<uint8_t>(N));  // 1 byte for object + size
                 }
                 else if (N <= 0xff)
                 {