diff --git a/src/bacnet/basic/bbmd6/vmac.c b/src/bacnet/basic/bbmd6/vmac.c
index 5a69b65b..b8e8be64 100644
--- a/src/bacnet/basic/bbmd6/vmac.c
+++ b/src/bacnet/basic/bbmd6/vmac.c
@@ -241,10 +241,7 @@ bool VMAC_Find_By_Data(struct vmac_data *vmac, uint32_t *device_id)
         list_vmac = Keylist_Data_Index(VMAC_List, index);
         if (list_vmac) {
             if (VMAC_Match(vmac, list_vmac)) {
-                if (device_id) {
-                    *device_id = Keylist_Key(VMAC_List, index);
-                }
-                status = true;
+                status = Keylist_Index_Key(VMAC_List, index, device_id);
                 break;
             }
         }
@@ -260,24 +257,25 @@ bool VMAC_Find_By_Data(struct vmac_data *vmac, uint32_t *device_id)
 void VMAC_Cleanup(void)
 {
     struct vmac_data *pVMAC;
-    uint32_t device_id;
     const int index = 0;
     unsigned i = 0;
 
     if (VMAC_List) {
         do {
-            device_id = Keylist_Key(VMAC_List, index);
-#if !PRINT_ENABLED
-            UNUSED(device_id);
+#if PRINT_ENABLED
+            uint32_t device_id;
+            Keylist_Index_Key(VMAC_List, index, &device_id);
 #endif
             pVMAC = Keylist_Data_Delete_By_Index(VMAC_List, index);
             if (pVMAC) {
+#if PRINT_ENABLED
                 PRINTF("VMAC List: %lu [", (unsigned long)device_id);
                 /* print the MAC */
                 for (i = 0; i < pVMAC->mac_len; i++) {
                     PRINTF("%02X", pVMAC->mac[i]);
                 }
                 PRINTF("]\n");
+#endif
                 free(pVMAC);
             }
         } while (pVMAC);
diff --git a/src/bacnet/basic/object/ao.c b/src/bacnet/basic/object/ao.c
index 1de3e1b6..fa2e3713 100644
--- a/src/bacnet/basic/object/ao.c
+++ b/src/bacnet/basic/object/ao.c
@@ -156,7 +156,11 @@ unsigned Analog_Output_Count(void)
  */
 uint32_t Analog_Output_Index_To_Instance(unsigned index)
 {
-    return Keylist_Key(Object_List, index);
+    KEY key = UINT32_MAX;
+
+    Keylist_Index_Key(Object_List, index, &key);
+
+    return key;
 }
 
 /**
diff --git a/src/bacnet/basic/object/bacfile.c b/src/bacnet/basic/object/bacfile.c
index 8f0a08b6..d6215f19 100644
--- a/src/bacnet/basic/object/bacfile.c
+++ b/src/bacnet/basic/object/bacfile.c
@@ -159,18 +159,20 @@ uint32_t bacfile_pathname_instance(
     struct object_data *pObject;
     int count = 0;
     int index = 0;
+    KEY key = BACNET_MAX_INSTANCE;
 
     count = Keylist_Count(Object_List);
     while (count) {
         pObject = Keylist_Data_Index(Object_List, index);
         if (strcmp(pathname, pObject->Pathname) == 0) {
-            return Keylist_Key(Object_List, index);
+            Keylist_Index_Key(Object_List, index, &key);
+            break;
         }
         count--;
         index++;
     }
 
-    return BACNET_MAX_INSTANCE;
+    return key;
 }
 
 /**
@@ -262,7 +264,11 @@ uint32_t bacfile_count(void)
  */
 uint32_t bacfile_index_to_instance(unsigned find_index)
 {
-    return Keylist_Key(Object_List, find_index);
+    KEY key = UINT32_MAX;
+
+    Keylist_Index_Key(Object_List, find_index, &key);
+
+    return key;
 }
 
 /**
diff --git a/src/bacnet/basic/object/blo.c b/src/bacnet/basic/object/blo.c
index f437473e..8f53e7d4 100644
--- a/src/bacnet/basic/object/blo.c
+++ b/src/bacnet/basic/object/blo.c
@@ -143,7 +143,11 @@ unsigned Binary_Lighting_Output_Count(void)
  */
 uint32_t Binary_Lighting_Output_Index_To_Instance(unsigned index)
 {
-    return Keylist_Key(Object_List, index);
+    KEY key = UINT32_MAX;
+
+    Keylist_Index_Key(Object_List, index, &key);
+
+    return key;
 }
 
 /**
diff --git a/src/bacnet/basic/object/bo.c b/src/bacnet/basic/object/bo.c
index 58946afe..a170af37 100644
--- a/src/bacnet/basic/object/bo.c
+++ b/src/bacnet/basic/object/bo.c
@@ -159,7 +159,11 @@ unsigned Binary_Output_Count(void)
  */
 uint32_t Binary_Output_Index_To_Instance(unsigned index)
 {
-    return Keylist_Key(Object_List, index);
+    KEY key = UINT32_MAX;
+
+    Keylist_Index_Key(Object_List, index, &key);
+
+    return key;
 }
 
 /**
diff --git a/src/bacnet/basic/object/calendar.c b/src/bacnet/basic/object/calendar.c
index 8379c324..e893c896 100644
--- a/src/bacnet/basic/object/calendar.c
+++ b/src/bacnet/basic/object/calendar.c
@@ -133,7 +133,11 @@ unsigned Calendar_Count(void)
  */
 uint32_t Calendar_Index_To_Instance(unsigned index)
 {
-    return Keylist_Key(Object_List, index);
+    KEY key = UINT32_MAX;
+
+    Keylist_Index_Key(Object_List, index, &key);
+
+    return key;
 }
 
 /**
diff --git a/src/bacnet/basic/object/channel.c b/src/bacnet/basic/object/channel.c
index 6a3e6ca7..1e74c8b3 100644
--- a/src/bacnet/basic/object/channel.c
+++ b/src/bacnet/basic/object/channel.c
@@ -154,7 +154,11 @@ unsigned Channel_Count(void)
  */
 uint32_t Channel_Index_To_Instance(unsigned index)
 {
-    return Keylist_Key(Object_List, index);
+    KEY key = UINT32_MAX;
+
+    Keylist_Index_Key(Object_List, index, &key);
+
+    return key;
 }
 
 /**
diff --git a/src/bacnet/basic/object/color_object.c b/src/bacnet/basic/object/color_object.c
index 8b7ce2b7..76b31741 100644
--- a/src/bacnet/basic/object/color_object.c
+++ b/src/bacnet/basic/object/color_object.c
@@ -148,7 +148,11 @@ unsigned Color_Count(void)
  */
 uint32_t Color_Index_To_Instance(unsigned index)
 {
-    return Keylist_Key(Object_List, index);
+    KEY key = UINT32_MAX;
+
+    Keylist_Index_Key(Object_List, index, &key);
+
+    return key;
 }
 
 /**
diff --git a/src/bacnet/basic/object/color_temperature.c b/src/bacnet/basic/object/color_temperature.c
index 09914b0f..fec53797 100644
--- a/src/bacnet/basic/object/color_temperature.c
+++ b/src/bacnet/basic/object/color_temperature.c
@@ -144,7 +144,11 @@ unsigned Color_Temperature_Count(void)
  */
 uint32_t Color_Temperature_Index_To_Instance(unsigned index)
 {
-    return Keylist_Key(Object_List, index);
+    KEY key = UINT32_MAX;
+
+    Keylist_Index_Key(Object_List, index, &key);
+
+    return key;
 }
 
 /**
diff --git a/src/bacnet/basic/object/lo.c b/src/bacnet/basic/object/lo.c
index f44f4618..2e9b9f4a 100644
--- a/src/bacnet/basic/object/lo.c
+++ b/src/bacnet/basic/object/lo.c
@@ -174,7 +174,11 @@ unsigned Lighting_Output_Count(void)
  */
 uint32_t Lighting_Output_Index_To_Instance(unsigned index)
 {
-    return Keylist_Key(Object_List, index);
+    KEY key = UINT32_MAX;
+
+    Keylist_Index_Key(Object_List, index, &key);
+
+    return key;
 }
 
 /**
diff --git a/src/bacnet/basic/object/lsp.c b/src/bacnet/basic/object/lsp.c
index a29fa685..e14c60d4 100644
--- a/src/bacnet/basic/object/lsp.c
+++ b/src/bacnet/basic/object/lsp.c
@@ -133,7 +133,11 @@ unsigned Life_Safety_Point_Count(void)
  */
 uint32_t Life_Safety_Point_Index_To_Instance(unsigned index)
 {
-    return Keylist_Key(Object_List, index);
+    KEY key = UINT32_MAX;
+
+    Keylist_Index_Key(Object_List, index, &key);
+
+    return key;
 }
 
 /**
diff --git a/src/bacnet/basic/object/mso.c b/src/bacnet/basic/object/mso.c
index d60d3168..ac94de13 100644
--- a/src/bacnet/basic/object/mso.c
+++ b/src/bacnet/basic/object/mso.c
@@ -150,7 +150,11 @@ unsigned Multistate_Output_Count(void)
  */
 uint32_t Multistate_Output_Index_To_Instance(unsigned index)
 {
-    return Keylist_Key(Object_List, index);
+    KEY key = UINT32_MAX;
+
+    Keylist_Index_Key(Object_List, index, &key);
+
+    return key;
 }
 
 /**
diff --git a/src/bacnet/basic/object/time_value.c b/src/bacnet/basic/object/time_value.c
index 72af1b3d..05a0ed65 100644
--- a/src/bacnet/basic/object/time_value.c
+++ b/src/bacnet/basic/object/time_value.c
@@ -136,7 +136,11 @@ unsigned Time_Value_Count(void)
  */
 uint32_t Time_Value_Index_To_Instance(unsigned index)
 {
-    return Keylist_Key(Object_List, index);
+    KEY key = UINT32_MAX;
+
+    Keylist_Index_Key(Object_List, index, &key);
+
+    return key;
 }
 
 /**
diff --git a/src/bacnet/basic/sys/keylist.c b/src/bacnet/basic/sys/keylist.c
index 99c5ca6a..9e4c6fd5 100644
--- a/src/bacnet/basic/sys/keylist.c
+++ b/src/bacnet/basic/sys/keylist.c
@@ -41,16 +41,9 @@
 /* static data */
 
 #include <stdlib.h>
-
-#include "bacnet/basic/sys/keylist.h" /* check for valid prototypes */
-
-#ifndef FALSE
-#define FALSE 0
-#endif
-
-#ifndef TRUE
-#define TRUE 1
-#endif
+#include <stdint.h>
+#include <stdbool.h>
+#include "bacnet/basic/sys/keylist.h"
 
 /******************************************************************** */
 /* Generic node routines */
@@ -81,16 +74,16 @@ static struct Keylist *KeylistCreate(void)
  *
  * @param list  Pointer to the list to be tested.
  *
- * @return Returns TRUE if success, FALSE if failed
+ * @return Returns true if success, false if failed
  */
-static int CheckArraySize(OS_Keylist list)
+static bool CheckArraySize(OS_Keylist list)
 {
     int new_size = 0; /* set it up so that no size change is the default */
     const int chunk = 8; /* minimum number of nodes to allocate memory for */
     struct Keylist_Node **new_array = NULL; /* new array of nodes, if needed */
     int i; /* counter */
     if (!list) {
-        return FALSE;
+        return false;
     }
 
     /* indicates the need for more memory allocation */
@@ -107,7 +100,7 @@ static int CheckArraySize(OS_Keylist list)
 
         /* See if we got the memory we wanted */
         if (!new_array) {
-            return FALSE;
+            return true;
         }
 
         /* copy the nodes from the old array to the new array */
@@ -121,12 +114,12 @@ static int CheckArraySize(OS_Keylist list)
         list->size = new_size;
     }
 
-    return TRUE;
+    return true;
 }
 
 /** Find the index of the key that we are looking for.
  * Since it is sorted, we can optimize the search.
- * returns TRUE if found, and FALSE not found.
+ * returns true if found, and false not found.
  * Returns the found key and the index where it was found in parameters.
  * If the key is not found, the nearest index from the bottom will be returned,
  * allowing the ability to find where an key should go into the list.
@@ -136,24 +129,24 @@ static int CheckArraySize(OS_Keylist list)
  * @param pIndex  Pointer to the variable taking the index were the key
  *                had been found.
  *
- * @return TRUE if found, and FALSE if not
+ * @return true if found, and false if not
  */
-static int FindIndex(OS_Keylist list, KEY key, int *pIndex)
+static bool FindIndex(OS_Keylist list, KEY key, int *pIndex)
 {
     struct Keylist_Node *node; /* holds the new node */
     int left = 0; /* the left branch of tree, beginning of list */
     int right = 0; /* the right branch on the tree, end of list */
     int index = 0; /* our current search place in the array */
     KEY current_key = 0; /* place holder for current node key */
-    int status = FALSE; /* return value */
+    bool status = false; /* return value */
 
     if (!list) {
         *pIndex = 0;
-        return (FALSE);
+        return false;
     }
     if (!list->array || !list->count) {
         *pIndex = 0;
-        return (FALSE);
+        return false;
     }
     right = list->count - 1;
     /* assume that the list is sorted */
@@ -174,7 +167,7 @@ static int FindIndex(OS_Keylist list, KEY key, int *pIndex)
     } while ((key != current_key) && (left <= right));
 
     if (key == current_key) {
-        status = TRUE;
+        status = true;
         *pIndex = index;
 
     } else {
@@ -186,7 +179,7 @@ static int FindIndex(OS_Keylist list, KEY key, int *pIndex)
             *pIndex = index;
         }
     }
-    return (status);
+    return status;
 }
 
 /******************************************************************** */
@@ -398,11 +391,12 @@ void *Keylist_Data_Index(OS_Keylist list, int index)
  * @param list  Pointer to the list
  * @param index  Index that shall be returned
  *
- * @return Key for the index or 0.
+ * @return Key for the index or UINT32_MAX if not found.
+ * @deprecated Use Keylist_Index_Key() instead
  */
 KEY Keylist_Key(OS_Keylist list, int index)
 {
-    KEY key = 0; /* return value */
+    KEY key = UINT32_MAX; /* return value */
     struct Keylist_Node *node;
 
     if (list) {
@@ -417,6 +411,35 @@ KEY Keylist_Key(OS_Keylist list, int index)
     return key;
 }
 
+/** 
+ * Determine if there is a node key at the given index.
+ *
+ * @param list  Pointer to the list
+ * @param index  Index that shall be returned
+ * @param pKey  Pointer to the variable returning the key
+ * @return True if the key is found, false if not.
+ */
+bool Keylist_Index_Key(OS_Keylist list, int index, KEY *pKey)
+{
+    bool status = false; /* return value */
+    struct Keylist_Node *node;
+
+    if (list) {
+        if (list->array && list->count && (index >= 0) &&
+            (index < list->count)) {
+            node = list->array[index];
+            if (node) {
+                status = true;
+                if (pKey) {
+                    *pKey = node->key;
+                }
+            }
+        }
+    }
+
+    return status;
+}
+
 /** Returns the next empty key from the list.
  *
  * @param list  Pointer to the list
diff --git a/src/bacnet/basic/sys/keylist.h b/src/bacnet/basic/sys/keylist.h
index 940c5117..5be3eff9 100644
--- a/src/bacnet/basic/sys/keylist.h
+++ b/src/bacnet/basic/sys/keylist.h
@@ -25,6 +25,7 @@
 #define KEYLIST_H
 
 #include "bacnet/bacnet_stack_exports.h"
+#include "bacnet/basic/sys/platform.h"
 #include "bacnet/basic/sys/key.h"
 
 /* This is a key sorted linked list data library that */
@@ -104,12 +105,20 @@ extern "C" {
         OS_Keylist list,
         int index);
 
-/* return the key at the given index */
+/* returns the node key specified by the index */
+    BACNET_STACK_DEPRECATED("Use Keylist_Index_Key() instead")
     BACNET_STACK_EXPORT
     KEY Keylist_Key(
         OS_Keylist list,
         int index);
 
+/* returns the node key specified by the index */
+    BACNET_STACK_EXPORT
+    bool Keylist_Index_Key(
+        OS_Keylist list, 
+        int index, 
+        KEY *pKey);
+
 /* returns the next empty key from the list */
     BACNET_STACK_EXPORT
     KEY Keylist_Next_Empty_Key(
diff --git a/test/bacnet/basic/sys/keylist/src/main.c b/test/bacnet/basic/sys/keylist/src/main.c
index 787d39b4..b44e012e 100644
--- a/test/bacnet/basic/sys/keylist/src/main.c
+++ b/test/bacnet/basic/sys/keylist/src/main.c
@@ -122,6 +122,7 @@ ZTEST(keylist_tests, testKeyListDataKey)
 static void testKeyListDataKey(void)
 #endif
 {
+    bool status = false;
     OS_Keylist list;
     KEY key;
     KEY test_key;
@@ -137,19 +138,22 @@ static void testKeyListDataKey(void)
     key = 1;
     index = Keylist_Data_Add(list, key, data1);
     zassert_equal(index, 0, NULL);
-    test_key = Keylist_Key(list, index);
+    status = Keylist_Index_Key(list, index, &test_key);
+    zassert_true(status, NULL);
     zassert_equal(test_key, key, NULL);
 
     key = 2;
     index = Keylist_Data_Add(list, key, data2);
     zassert_equal(index, 1, NULL);
-    test_key = Keylist_Key(list, index);
+    status = Keylist_Index_Key(list, index, &test_key);
+    zassert_true(status, NULL);
     zassert_equal(test_key, key, NULL);
 
     key = 3;
     index = Keylist_Data_Add(list, key, data3);
     zassert_equal(index, 2, NULL);
-    test_key = Keylist_Key(list, index);
+    status = Keylist_Index_Key(list, index, &test_key);
+    zassert_true(status, NULL);
     zassert_equal(test_key, key, NULL);
 
     zassert_equal(Keylist_Count(list), 3, NULL);
@@ -278,7 +282,8 @@ ZTEST(keylist_tests, testKeyListLarge)
 static void testKeyListLarge(void)
 #endif
 {
-    int data1 = 42;
+    bool status = false;
+    int data_list[1024 * 16] = { 0 };
     int *data;
     OS_Keylist list;
     KEY key;
@@ -290,15 +295,18 @@ static void testKeyListLarge(void)
         return;
 
     for (key = 0; key < num_keys; key++) {
-        index = Keylist_Data_Add(list, key, &data1);
+        data_list[key] = 42 + key;
+        index = Keylist_Data_Add(list, key, &data_list[key]);
     }
     for (key = 0; key < num_keys; key++) {
         data = Keylist_Data(list, key);
-        zassert_equal(*data, data1, NULL);
+        zassert_equal(*data, data_list[key], NULL);
     }
     for (index = 0; index < num_keys; index++) {
         data = Keylist_Data_Index(list, index);
-        zassert_equal(*data, data1, NULL);
+        status = Keylist_Index_Key(list, index, &key);
+        zassert_true(status, NULL);
+        zassert_equal(*data, data_list[key], NULL);
     }
     Keylist_Delete(list);