diff --git a/src/qcbor_err_to_str.c b/src/qcbor_err_to_str.c
index 4879f91..87c2b28 100644
--- a/src/qcbor_err_to_str.c
+++ b/src/qcbor_err_to_str.c
@@ -1,69 +1,92 @@
-/*==============================================================================
- err_to_str.c -- strings names for errors
-
- Copyright (c) 2020, Patrick Uiterwijk. All rights reserved.
- Copyright (c) 2020, Laurence Lundblade.
- Copyright (c) 2021, Arm Limited. All rights reserved.
-
- SPDX-License-Identifier: BSD-3-Clause
-
- See BSD-3-Clause license in README.md
-
- Created on 3/21/20
- =============================================================================*/
+/* ==========================================================================
+ * err_to_str.c -- strings names for errors
+ *
+ * Copyright (c) 2020, Patrick Uiterwijk. All rights reserved.
+ * Copyright (c) 2020,2024, Laurence Lundblade.
+ * Copyright (c) 2021, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ * See BSD-3-Clause license in README.md
+ *
+ * Created on 3/21/20
+ * ========================================================================== */
 
 #include "qcbor/qcbor_common.h"
+#include <string.h>
 
-#define _ERR_TO_STR(errpart) case QCBOR_##errpart: return "QCBOR_" #errpart;
+#define ERR_TO_STR_CASE(errpart) case errpart: return #errpart;
 
-const char *qcbor_err_to_str(QCBORError err) {
-    switch (err) {
-    _ERR_TO_STR(SUCCESS)
-    _ERR_TO_STR(ERR_BUFFER_TOO_SMALL)
-    _ERR_TO_STR(ERR_ENCODE_UNSUPPORTED)
-    _ERR_TO_STR(ERR_BUFFER_TOO_LARGE)
-    _ERR_TO_STR(ERR_ARRAY_NESTING_TOO_DEEP)
-    _ERR_TO_STR(ERR_CLOSE_MISMATCH)
-    _ERR_TO_STR(ERR_ARRAY_TOO_LONG)
-    _ERR_TO_STR(ERR_TOO_MANY_CLOSES)
-    _ERR_TO_STR(ERR_ARRAY_OR_MAP_STILL_OPEN)
-    _ERR_TO_STR(ERR_BAD_TYPE_7)
-    _ERR_TO_STR(ERR_EXTRA_BYTES)
-    _ERR_TO_STR(ERR_UNSUPPORTED)
-    _ERR_TO_STR(ERR_ARRAY_OR_MAP_UNCONSUMED)
-    _ERR_TO_STR(ERR_BAD_INT)
-    _ERR_TO_STR(ERR_INDEFINITE_STRING_CHUNK)
-    _ERR_TO_STR(ERR_HIT_END)
-    _ERR_TO_STR(ERR_BAD_BREAK)
-    _ERR_TO_STR(ERR_INPUT_TOO_LARGE)
-    _ERR_TO_STR(ERR_ARRAY_DECODE_NESTING_TOO_DEEP)
-    _ERR_TO_STR(ERR_ARRAY_DECODE_TOO_LONG)
-    _ERR_TO_STR(ERR_STRING_TOO_LONG)
-    _ERR_TO_STR(ERR_BAD_EXP_AND_MANTISSA)
-    _ERR_TO_STR(ERR_NO_STRING_ALLOCATOR)
-    _ERR_TO_STR(ERR_STRING_ALLOCATE)
-    _ERR_TO_STR(ERR_TOO_MANY_TAGS)
-    _ERR_TO_STR(ERR_MAP_LABEL_TYPE)
-    _ERR_TO_STR(ERR_UNEXPECTED_TYPE)
-    _ERR_TO_STR(ERR_BAD_OPT_TAG)
-    _ERR_TO_STR(ERR_DUPLICATE_LABEL)
-    _ERR_TO_STR(ERR_MEM_POOL_SIZE)
-    _ERR_TO_STR(ERR_INT_OVERFLOW)
-    _ERR_TO_STR(ERR_DATE_OVERFLOW)
-    _ERR_TO_STR(ERR_EXIT_MISMATCH)
-    _ERR_TO_STR(ERR_NO_MORE_ITEMS)
-    _ERR_TO_STR(ERR_LABEL_NOT_FOUND)
-    _ERR_TO_STR(ERR_NUMBER_SIGN_CONVERSION)
-    _ERR_TO_STR(ERR_CONVERSION_UNDER_OVER_FLOW)
-    _ERR_TO_STR(ERR_MAP_NOT_ENTERED)
-    _ERR_TO_STR(ERR_CALLBACK_FAIL)
-    _ERR_TO_STR(ERR_FLOAT_DATE_DISABLED)
-    _ERR_TO_STR(ERR_HALF_PRECISION_DISABLED)
-    _ERR_TO_STR(ERR_HW_FLOAT_DISABLED)
-    _ERR_TO_STR(ERR_FLOAT_EXCEPTION)
-    _ERR_TO_STR(ERR_ALL_FLOAT_DISABLED)
 
-    default:
-        return "Unidentified error";
-    }
+const char *
+qcbor_err_to_str(const QCBORError uErr) {
+   switch (uErr) {
+   ERR_TO_STR_CASE(QCBOR_SUCCESS)
+   ERR_TO_STR_CASE(QCBOR_ERR_BUFFER_TOO_SMALL)
+   ERR_TO_STR_CASE(QCBOR_ERR_ENCODE_UNSUPPORTED)
+   ERR_TO_STR_CASE(QCBOR_ERR_BUFFER_TOO_LARGE)
+   ERR_TO_STR_CASE(QCBOR_ERR_ARRAY_NESTING_TOO_DEEP)
+   ERR_TO_STR_CASE(QCBOR_ERR_CLOSE_MISMATCH)
+   ERR_TO_STR_CASE(QCBOR_ERR_ARRAY_TOO_LONG)
+   ERR_TO_STR_CASE(QCBOR_ERR_TOO_MANY_CLOSES)
+   ERR_TO_STR_CASE(QCBOR_ERR_ARRAY_OR_MAP_STILL_OPEN)
+   ERR_TO_STR_CASE(QCBOR_ERR_OPEN_BYTE_STRING)
+   ERR_TO_STR_CASE(QCBOR_ERR_CANNOT_CANCEL)
+   ERR_TO_STR_CASE(QCBOR_ERR_BAD_TYPE_7)
+   ERR_TO_STR_CASE(QCBOR_ERR_EXTRA_BYTES)
+   ERR_TO_STR_CASE(QCBOR_ERR_UNSUPPORTED)
+   ERR_TO_STR_CASE(QCBOR_ERR_ARRAY_OR_MAP_UNCONSUMED)
+   ERR_TO_STR_CASE(QCBOR_ERR_BAD_INT)
+   ERR_TO_STR_CASE(QCBOR_ERR_INDEFINITE_STRING_CHUNK)
+   ERR_TO_STR_CASE(QCBOR_ERR_HIT_END)
+   ERR_TO_STR_CASE(QCBOR_ERR_BAD_BREAK)
+   ERR_TO_STR_CASE(QCBOR_ERR_INPUT_TOO_LARGE)
+   ERR_TO_STR_CASE(QCBOR_ERR_ARRAY_DECODE_NESTING_TOO_DEEP)
+   ERR_TO_STR_CASE(QCBOR_ERR_ARRAY_DECODE_TOO_LONG)
+   ERR_TO_STR_CASE(QCBOR_ERR_STRING_TOO_LONG)
+   ERR_TO_STR_CASE(QCBOR_ERR_BAD_EXP_AND_MANTISSA)
+   ERR_TO_STR_CASE(QCBOR_ERR_NO_STRING_ALLOCATOR)
+   ERR_TO_STR_CASE(QCBOR_ERR_STRING_ALLOCATE)
+   ERR_TO_STR_CASE(QCBOR_ERR_MAP_LABEL_TYPE)
+   ERR_TO_STR_CASE(QCBOR_ERR_UNRECOVERABLE_TAG_CONTENT)
+   ERR_TO_STR_CASE(QCBOR_ERR_INDEF_LEN_STRINGS_DISABLED)
+   ERR_TO_STR_CASE(QCBOR_ERR_INDEF_LEN_ARRAYS_DISABLED)
+   ERR_TO_STR_CASE(QCBOR_ERR_TAGS_DISABLED)
+   ERR_TO_STR_CASE(QCBOR_ERR_TOO_MANY_TAGS)
+   ERR_TO_STR_CASE(QCBOR_ERR_UNEXPECTED_TYPE)
+   ERR_TO_STR_CASE(QCBOR_ERR_DUPLICATE_LABEL)
+   ERR_TO_STR_CASE(QCBOR_ERR_MEM_POOL_SIZE)
+   ERR_TO_STR_CASE(QCBOR_ERR_INT_OVERFLOW)
+   ERR_TO_STR_CASE(QCBOR_ERR_DATE_OVERFLOW)
+   ERR_TO_STR_CASE(QCBOR_ERR_EXIT_MISMATCH)
+   ERR_TO_STR_CASE(QCBOR_ERR_NO_MORE_ITEMS)
+   ERR_TO_STR_CASE(QCBOR_ERR_LABEL_NOT_FOUND)
+   ERR_TO_STR_CASE(QCBOR_ERR_NUMBER_SIGN_CONVERSION)
+   ERR_TO_STR_CASE(QCBOR_ERR_CONVERSION_UNDER_OVER_FLOW)
+   ERR_TO_STR_CASE(QCBOR_ERR_MAP_NOT_ENTERED)
+   ERR_TO_STR_CASE(QCBOR_ERR_CALLBACK_FAIL)
+   ERR_TO_STR_CASE(QCBOR_ERR_FLOAT_DATE_DISABLED)
+   ERR_TO_STR_CASE(QCBOR_ERR_HALF_PRECISION_DISABLED)
+   ERR_TO_STR_CASE(QCBOR_ERR_HW_FLOAT_DISABLED)
+   ERR_TO_STR_CASE(QCBOR_ERR_FLOAT_EXCEPTION)
+   ERR_TO_STR_CASE(QCBOR_ERR_ALL_FLOAT_DISABLED)
+   ERR_TO_STR_CASE(QCBOR_ERR_RECOVERABLE_BAD_TAG_CONTENT)
+   ERR_TO_STR_CASE(QCBOR_ERR_CANNOT_ENTER_ALLOCATED_STRING)
+
+   default:
+      if(uErr >= QCBOR_ERR_FIRST_USER_DEFINED && uErr <= QCBOR_ERR_LAST_USER_DEFINED) {
+         /* Static buffer is not thread safe, but this is only a diagnostic */
+         static char buf[20];
+         strcpy(buf, "USER_DEFINED_");
+         size_t uEndOffset = strlen(buf);
+         buf[uEndOffset]   = (char)(uErr/100 + '0');
+         buf[uEndOffset+1] = (char)(((uErr/10) % 10) + '0');
+         buf[uEndOffset+2] = (char)((uErr % 10 )+ '0');
+         buf[uEndOffset+3] = '\0';
+         return buf;
+
+      } else {
+         return "Unidentified QCBOR error";
+      }
+   }
 }