diff --git a/bacnet-stack/include/bacstr.h b/bacnet-stack/include/bacstr.h
index 100298ff..19f05236 100644
--- a/bacnet-stack/include/bacstr.h
+++ b/bacnet-stack/include/bacstr.h
@@ -38,16 +38,15 @@
 #include <stdbool.h>
 #include <stddef.h>
 #include "bacdef.h"
+#include "config.h"
 
 /* bit strings
    They could be as large as 256/8=32 octets */
-#define MAX_BITSTRING_BYTES 15
 typedef struct BACnet_Bit_String {
     uint8_t bits_used;
     uint8_t value[MAX_BITSTRING_BYTES];
 } BACNET_BIT_STRING;
 
-#define MAX_CHARACTER_STRING_BYTES (MAX_APDU-6)
 typedef struct BACnet_Character_String {
     size_t length;
     uint8_t encoding;
@@ -60,7 +59,7 @@ typedef struct BACnet_Character_String {
 typedef struct BACnet_Octet_String {
     size_t length;
     /* limit - 6 octets is the most our tag and type could be */
-    uint8_t value[MAX_APDU - 6];
+    uint8_t value[MAX_OCTET_STRING_BYTES];
 } BACNET_OCTET_STRING;
 
 #ifdef __cplusplus
diff --git a/bacnet-stack/include/config.h b/bacnet-stack/include/config.h
index 97c96f29..7f709f1f 100644
--- a/bacnet-stack/include/config.h
+++ b/bacnet-stack/include/config.h
@@ -134,4 +134,10 @@
 #define BACAPP_OBJECT_ID
 #endif
 
+/*
+** Set the maximum vector type sizes
+*/
+#define MAX_BITSTRING_BYTES        (15)
+#define MAX_CHARACTER_STRING_BYTES (MAX_APDU-6)
+#define MAX_OCTET_STRING_BYTES     (MAX_APDU-6)
 #endif
diff --git a/bacnet-stack/src/bacstr.c b/bacnet-stack/src/bacstr.c
index 8db0378e..647c69ea 100644
--- a/bacnet-stack/src/bacstr.c
+++ b/bacnet-stack/src/bacstr.c
@@ -167,7 +167,7 @@ uint8_t bitstring_bits_capacity(
     BACNET_BIT_STRING * bit_string)
 {
     if (bit_string) {
-        return (sizeof(bit_string->value) * 8);
+        return (MAX_BITSTRING_BYTES * 8);
     } else {
         return 0;
     }
@@ -420,7 +420,7 @@ uint8_t characterstring_encoding(
 }
 
 /* returns false if the string exceeds capacity
-   initialize by using length=0 */
+   initialize by using value=0 */
 bool octetstring_init(
     BACNET_OCTET_STRING * octet_string,
     uint8_t * value,
@@ -431,17 +431,18 @@ bool octetstring_init(
 
     if (octet_string) {
         octet_string->length = 0;
-        if (length <= sizeof(octet_string->value)) {
-            if (value) {
-                for (i = 0; i < length; i++) {
-                    octet_string->value[octet_string->length] = value[i];
-                    octet_string->length++;
-                }
-            } else {
-                for (i = 0; i < sizeof(octet_string->value); i++) {
-                    octet_string->value[i] = 0;
-                }
-            }
+		if (value) {
+			if (length <= MAX_OCTET_STRING_BYTES) {
+				for (i = 0; i < length; i++) {
+					octet_string->value[octet_string->length] = value[i];
+					octet_string->length++;
+				}
+				status = true;
+			}
+		} else {
+			for (i = 0; i < MAX_OCTET_STRING_BYTES; i++) {
+				octet_string->value[i] = 0;
+			}
             status = true;
         }
     }
@@ -467,7 +468,7 @@ bool octetstring_append(
     bool status = false;        /* return value */
 
     if (octet_string) {
-        if ((length + octet_string->length) <= sizeof(octet_string->value)) {
+        if ((length + octet_string->length) <= MAX_OCTET_STRING_BYTES) {
             for (i = 0; i < length; i++) {
                 octet_string->value[octet_string->length] = value[i];
                 octet_string->length++;
@@ -489,7 +490,7 @@ bool octetstring_truncate(
     bool status = false;        /* return value */
 
     if (octet_string) {
-        if (length <= sizeof(octet_string->value)) {
+        if (length <= MAX_OCTET_STRING_BYTES) {
             octet_string->length = length;
             status = true;
         }
@@ -533,7 +534,7 @@ size_t octetstring_capacity(
 
     if (octet_string) {
         /* FIXME: validate length is within bounds? */
-        length = sizeof(octet_string->value);
+        length = MAX_OCTET_STRING_BYTES;
     }
 
     return length;
@@ -548,7 +549,7 @@ bool octetstring_value_same(
 
     if (octet_string1 && octet_string2) {
         if ((octet_string1->length == octet_string2->length) &&
-            (octet_string1->length <= sizeof(octet_string1->value))) {
+            (octet_string1->length <= MAX_OCTET_STRING_BYTES)) {
             for (i = 0; i < octet_string1->length; i++) {
                 if (octet_string1->value[i] != octet_string2->value[i]) {
                     return false;