diff --git a/dynaml/concatenation.go b/dynaml/concatenation.go
index c646a5f..354723f 100644
--- a/dynaml/concatenation.go
+++ b/dynaml/concatenation.go
@@ -20,15 +20,17 @@ func (e ConcatenationExpr) Evaluate(binding Binding) (yaml.Node, bool) {
 		return nil, false
 	}
 
-	astring, ok := a.(string)
-	if !ok {
-		return nil, false
+	astring, aok := a.(string)
+	bstring, bok := b.(string)
+	if aok && bok {
+		return astring + bstring, true
 	}
 
-	bstring, ok := b.(string)
-	if !ok {
-		return nil, false
+	alist, aok := a.([]yaml.Node)
+	blist, bok := b.([]yaml.Node)
+	if aok && bok {
+		return append(alist, blist...), true
 	}
 
-	return astring + bstring, true
+	return nil, false
 }
diff --git a/dynaml/concatenation_test.go b/dynaml/concatenation_test.go
index 5db2092..c7449ab 100644
--- a/dynaml/concatenation_test.go
+++ b/dynaml/concatenation_test.go
@@ -1,39 +1,58 @@
 package dynaml
 
 import (
+	"github.com/vito/spiff/yaml"
+
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
 )
 
 var _ = Describe("concatenation", func() {
-	It("concatenates two strings", func() {
-		expr := ConcatenationExpr{
-			StringExpr{"one"},
-			StringExpr{"two"},
-		}
+	Context("when the left-hand side is a string", func() {
+		Context("and the right-hand side is a string", func() {
+			It("concatenates both strings", func() {
+				expr := ConcatenationExpr{
+					StringExpr{"one"},
+					StringExpr{"two"},
+				}
 
-		Expect(expr).To(EvaluateAs("onetwo", FakeBinding{}))
-	})
+				Expect(expr).To(EvaluateAs("onetwo", FakeBinding{}))
+			})
+		})
 
-	Context("when the left-hand side is not a string", func() {
-		It("fails", func() {
-			expr := ConcatenationExpr{
-				StringExpr{"one"},
-				IntegerExpr{42},
-			}
+		Context("and the right-hand side is NOT a string", func() {
+			It("fails", func() {
+				expr := ConcatenationExpr{
+					StringExpr{"two"},
+					IntegerExpr{42},
+				}
 
-			Expect(expr).To(FailToEvaluate(FakeBinding{}))
+				Expect(expr).To(FailToEvaluate(FakeBinding{}))
+			})
 		})
 	})
 
-	Context("when the right-hand side is not a string", func() {
-		It("fails", func() {
-			expr := ConcatenationExpr{
-				IntegerExpr{42},
-				StringExpr{"two"},
-			}
+	Context("when the left-hand side is a list", func() {
+		Context("and the right-hand side is a list", func() {
+			It("concatenates both lists", func() {
+				expr := ConcatenationExpr{
+					ListExpr{[]Expression{StringExpr{"one"}}},
+					ListExpr{[]Expression{StringExpr{"two"}}},
+				}
+
+				Expect(expr).To(EvaluateAs([]yaml.Node{"one", "two"}, FakeBinding{}))
+			})
+		})
+
+		Context("and the right-hand side is NOT a list", func() {
+			It("fails", func() {
+				expr := ConcatenationExpr{
+					IntegerExpr{42},
+					ListExpr{[]Expression{StringExpr{"two"}}},
+				}
 
-			Expect(expr).To(FailToEvaluate(FakeBinding{}))
+				Expect(expr).To(FailToEvaluate(FakeBinding{}))
+			})
 		})
 	})
 })
diff --git a/spiff_test.go b/spiff_test.go
index 7b319d9..3793323 100644
--- a/spiff_test.go
+++ b/spiff_test.go
@@ -48,7 +48,6 @@ foo: bar
 				Expect(err).NotTo(HaveOccured())
 			})
 
-
 			It("resolves the template and prints it out", func() {
 				Expect(merge).To(Say(`foo: bar`))
 				Expect(merge).To(ExitWith(0))