diff --git a/sma.hh b/sma.hh
index aaac5e1..5000c76 100644
--- a/sma.hh
+++ b/sma.hh
@@ -85,6 +85,9 @@ class SMA4
 	struct Add { TYPE operator () (TYPE a, TYPE b) { return a + b; } };
 	SWA<TYPE, Add, NUM> swa;
 public:
+	SMA4() : swa(0)
+	{
+	}
 	TYPE operator () (TYPE input)
 	{
 		if (NORM)
diff --git a/swa.hh b/swa.hh
index c92e649..9909232 100644
--- a/swa.hh
+++ b/swa.hh
@@ -15,10 +15,10 @@ class SWA
 	int leaf;
 	OP op;
 public:
-	SWA() : leaf(NUM)
+	SWA(TYPE ident) : leaf(NUM)
 	{
 		for (int i = 0; i < 2 * NUM; ++i)
-			tree[i] = 0;
+			tree[i] = ident;
 	}
 	TYPE operator () (TYPE input)
 	{