diff --git a/CHANGES b/CHANGES
index c51cd00bbf..355b58f8fc 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,4 +1,8 @@
 
+2.5-852 | 2018-08-17 15:15:55 -0500
+
+  * BIT-466: add redef += support to vectors (Jon Siwek, Corelight)
+
 2.5-850 | 2018-08-17 11:12:53 -0500
 
   * BIT-1815: move SMB::write_cmd_log functionality into policy/ script
diff --git a/NEWS b/NEWS
index e5f5b28054..bb9ea619c8 100644
--- a/NEWS
+++ b/NEWS
@@ -314,6 +314,9 @@ New Functionality
 
 - An expression of the form "v += e" will append the value of the expression
   "e" to the end of the vector "v" (of course assuming type-compatbility).
+  "redef v += { a, b, c }" will similarly extend a vector previously declared
+  with &redef by appending the result of expressions "a", "b", and "c" to
+  the vector at initialization-time.
 
 Changed Functionality
 ---------------------
diff --git a/VERSION b/VERSION
index 3e949de53a..6aa99abe08 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-2.5-850
+2.5-852
diff --git a/src/ID.cc b/src/ID.cc
index a68abb6264..9e4eb7d245 100644
--- a/src/ID.cc
+++ b/src/ID.cc
@@ -140,10 +140,11 @@ void ID::SetVal(Val* v, init_class c)
 		}
 
 	if ( type->Tag() != TYPE_TABLE &&
-	     (type->Tag() != TYPE_PATTERN || c == INIT_REMOVE) )
+	     (type->Tag() != TYPE_PATTERN || c == INIT_REMOVE) &&
+	     (type->Tag() != TYPE_VECTOR  || c == INIT_REMOVE) )
 		{
 		if ( c == INIT_EXTRA )
-			Error("+= initializer only applies to tables, sets and patterns", v);
+			Error("+= initializer only applies to tables, sets, vectors and patterns", v);
 		else
 			Error("-= initializer only applies to tables and sets", v);
 		}
diff --git a/src/Val.cc b/src/Val.cc
index 7879d282b2..71d38e3c63 100644
--- a/src/Val.cc
+++ b/src/Val.cc
@@ -3321,6 +3321,29 @@ bool VectorVal::AssignRepeat(unsigned int index, unsigned int how_many,
 	return true;
 	}
 
+int VectorVal::AddTo(Val* val, int /* is_first_init */) const
+	{
+	if ( val->Type()->Tag() != TYPE_VECTOR )
+		{
+		val->Error("not a vector");
+		return 0;
+		}
+
+	VectorVal* v = val->AsVectorVal();
+
+	if ( ! same_type(type, v->Type()) )
+		{
+		type->Error("vector type clash", v->Type());
+		return 0;
+		}
+
+	auto last_idx = v->Size();
+
+	for ( auto i = 0u; i < Size(); ++i )
+		v->Assign(last_idx++, Lookup(i)->Ref());
+
+	return 1;
+	}
 
 Val* VectorVal::Lookup(unsigned int index) const
 	{
diff --git a/src/Val.h b/src/Val.h
index bb18dceb4f..f189668b28 100644
--- a/src/Val.h
+++ b/src/Val.h
@@ -1046,6 +1046,10 @@ public:
 	bool AssignRepeat(unsigned int index, unsigned int how_many,
 			  Val* element);
 
+	// Add this value to the given value (if appropriate).
+	// Returns true if succcessful.
+	int AddTo(Val* v, int is_first_init) const override;
+
 	// Returns nil if no element was at that value.
 	// Lookup does NOT grow the vector to this size.
 	// The Val* variant assumes that the index Val* has been type-checked.
diff --git a/testing/btest/Baseline/language.redef-vector/out b/testing/btest/Baseline/language.redef-vector/out
new file mode 100644
index 0000000000..73a5ef460d
--- /dev/null
+++ b/testing/btest/Baseline/language.redef-vector/out
@@ -0,0 +1,3 @@
+[testing, blah, foo, foo, testing]
+[one, two, three]
+[a, b, c, one, two, three, a, b, c, abc, d]
diff --git a/testing/btest/language/redef-vector.bro b/testing/btest/language/redef-vector.bro
new file mode 100644
index 0000000000..26dc2109ba
--- /dev/null
+++ b/testing/btest/language/redef-vector.bro
@@ -0,0 +1,18 @@
+# @TEST-EXEC: bro -b %INPUT >out
+# @TEST-EXEC: btest-diff out
+
+const foo: vector of string &redef;
+redef foo += { "testing", "blah", "foo", "foo", "testing" };
+
+const bar: vector of string = vector() &redef;
+redef bar += { "one", "two", "three" };
+
+const baz: vector of string = vector("a", "b", "c") &redef;
+redef baz += { "one", "two", "three" };
+redef baz += { "a", "b", "c" };
+const d = "d";
+redef baz += { "a" + "b" + "c", d };
+
+print foo;
+print bar;
+print baz;