diff --git a/src/mms/iso_mms/common/mms_type_spec.c b/src/mms/iso_mms/common/mms_type_spec.c
index 76c4cfea..5dd93c3f 100644
--- a/src/mms/iso_mms/common/mms_type_spec.c
+++ b/src/mms/iso_mms/common/mms_type_spec.c
@@ -138,10 +138,8 @@ MmsVariableSpecification_isValueOfType(MmsVariableSpecification* self, MmsValue*
             if (self->typeSpec.bitString == value->value.bitString.size)
                 return true;
 
-            if (self->typeSpec.bitString < 0) {
-                if (value->value.bitString.size <= (-self->typeSpec.bitString))
-                    return true;
-            }
+            if (self->typeSpec.bitString < 0)
+                return true;
         }
         else if (self->type == MMS_FLOAT) {
             if ((self->typeSpec.floatingpoint.exponentWidth == value->value.floatingPoint.exponentWidth) &&
diff --git a/src/mms/iso_mms/common/mms_value.c b/src/mms/iso_mms/common/mms_value.c
index 150798e4..88eda231 100644
--- a/src/mms/iso_mms/common/mms_value.c
+++ b/src/mms/iso_mms/common/mms_value.c
@@ -259,11 +259,14 @@ MmsValue_update(MmsValue* self, const MmsValue* update)
             case MMS_BIT_STRING:
                 if (self->value.bitString.size == update->value.bitString.size)
                     memcpy(self->value.bitString.buf, update->value.bitString.buf, bitStringByteSize(self));
-                else if (update->value.bitString.size < self->value.bitString.size) {
+                else if (update->value.bitString.size != self->value.bitString.size) {
                     int i;
 
                     for (i = 0; i < update->value.bitString.size; i++) {
-                        MmsValue_setBitStringBit(self, i, MmsValue_getBitStringBit(update, i));
+                        if (i < self->value.bitString.size)
+                            MmsValue_setBitStringBit(self, i, MmsValue_getBitStringBit(update, i));
+                        else
+                            break;
                     }
                 }
                 else