diff -r cf19b7820ff0 -r 94360453bce4 src/json.c
--- a/src/json.c	Thu Dec 25 12:07:37 2025 +0100
+++ b/src/json.c	Sun Dec 28 14:10:14 2025 +0100
@@ -96,20 +96,16 @@
 }
 
 static CxJsonToken token_create(CxJson *json, bool isstring, size_t start, size_t end) {
-    cxmutstr buf_str = cx_mutstrn(json->buffer.space + start, end - start);
-    cxmutstr str;
-    bool allocated;
+    cxmutstr str = cx_mutstrn(json->buffer.space + start, end - start);
+    bool allocated = false;
     if (json->uncompleted_tokentype != CX_JSON_NO_TOKEN) {
         allocated = true;
-        str = json->uncompleted_content;
-        if (cx_strcat(&str, 1, buf_str)) {
-            return (CxJsonToken){CX_JSON_NO_TOKEN, false, {NULL, 0}}; // LCOV_EXCL_LINE
+        str = cx_strcat(json->uncompleted_content, 1, str);
+        if (str.ptr == NULL) {
+            return (CxJsonToken){CX_JSON_NO_TOKEN, false, CX_NULLSTR}; // LCOV_EXCL_LINE
         }
-        json->uncompleted_content = (cxmutstr){NULL, 0};
+        json->uncompleted_content = CX_NULLSTR;
         json->uncompleted_tokentype = CX_JSON_NO_TOKEN;
-    } else {
-        allocated = false;
-        str = buf_str;
     }
     CxJsonTokenType ttype;
     if (isstring) {
@@ -126,7 +122,7 @@
         if (allocated) {
             cx_strfree(&str);
         }
-        return (CxJsonToken){CX_JSON_TOKEN_ERROR, false, {NULL, 0}};
+        return (CxJsonToken){CX_JSON_TOKEN_ERROR, false, CX_NULLSTR};
     }
     return (CxJsonToken){ttype, allocated, str};
 }
@@ -193,7 +189,7 @@
                 } else if (ctype != CX_JSON_NO_TOKEN) {
                     // single-char token
                     json->buffer.pos = i + 1;
-                    *result = (CxJsonToken){ctype, false, {NULL, 0}};
+                    *result = (CxJsonToken){ctype, false, CX_NULLSTR};
                     return CX_JSON_NO_ERROR;
                 } else {
                     ttype = CX_JSON_TOKEN_LITERAL; // number or literal
@@ -245,11 +241,13 @@
             }
             json->uncompleted_tokentype = ttype;
         } else {
-            // previously we also had an uncompleted token
+            // previously we already had an uncompleted token
             // combine the uncompleted token with the current token
-            if (cx_strcat(&json->uncompleted_content, 1, uncompleted)) {
+            cxmutstr s = cx_strcat(json->uncompleted_content, 1, uncompleted);
+            if (s.ptr == NULL) {
                 return CX_JSON_BUFFER_ALLOC_FAILED; // LCOV_EXCL_LINE
             }
+            json->uncompleted_content = s;
         }
         // advance the buffer position - we saved the stuff in the uncompleted token
         json->buffer.pos += uncompleted.length;
@@ -1429,14 +1427,14 @@
     CxBuffer buffer;
     if (cxBufferInit(&buffer, allocator, NULL, 128,
                      CX_BUFFER_AUTO_EXTEND | CX_BUFFER_DO_NOT_FREE)) {
-        return (cxmutstr){NULL, 0};
+        return CX_NULLSTR;
     }
     if (cx_json_write_rec(&buffer, value, cxBufferWriteFunc, writer, 0)
             || cxBufferTerminate(&buffer)) {
         // LCOV_EXCL_START
         buffer.flags &= ~CX_BUFFER_DO_NOT_FREE;
         cxBufferDestroy(&buffer);
-        return (cxmutstr){NULL, 0};
+        return CX_NULLSTR;
         // LCOV_EXCL_STOP
     } else {
         cxmutstr str = cx_bstr_m(&buffer);