diff --git a/terraform/context_validate_test.go b/terraform/context_validate_test.go
index 131955df3..9e434a7be 100644
--- a/terraform/context_validate_test.go
+++ b/terraform/context_validate_test.go
@@ -44,6 +44,28 @@ func TestContext2Validate_badVar(t *testing.T) {
 	}
 }
 
+func TestContext2Validate_varMapOverrideOld(t *testing.T) {
+	m := testModule(t, "validate-module-pc-vars")
+	p := testProvider("aws")
+	c := testContext2(t, &ContextOpts{
+		Module: m,
+		Providers: map[string]ResourceProviderFactory{
+			"aws": testProviderFuncFixed(p),
+		},
+		Variables: map[string]interface{}{
+			"foo.foo": "bar",
+		},
+	})
+
+	w, e := c.Validate()
+	if len(w) > 0 {
+		t.Fatalf("bad: %#v", w)
+	}
+	if len(e) == 0 {
+		t.Fatalf("bad: %s", e)
+	}
+}
+
 func TestContext2Validate_varNoDefaultExplicitType(t *testing.T) {
 	m := testModule(t, "validate-var-no-default-explicit-type")
 	c := testContext2(t, &ContextOpts{
diff --git a/terraform/semantics.go b/terraform/semantics.go
index 80ca636a8..6d99875cd 100644
--- a/terraform/semantics.go
+++ b/terraform/semantics.go
@@ -2,6 +2,7 @@ package terraform
 
 import (
 	"fmt"
+	"strings"
 
 	"github.com/hashicorp/go-multierror"
 	"github.com/hashicorp/terraform/config"
@@ -96,6 +97,21 @@ func smcUserVariables(c *config.Config, vs map[string]interface{}) []error {
 
 	// Check that types match up
 	for name, proposedValue := range vs {
+		// Check for "map.key" fields. These stopped working with Terraform
+		// 0.7 but we do this to surface a better error message informing
+		// the user what happened.
+		if idx := strings.Index(name, "."); idx > 0 {
+			key := name[:idx]
+			if _, ok := cvs[key]; ok {
+				errs = append(errs, fmt.Errorf(
+					"%s: Overriding map keys with the format `name.key` is no "+
+						"longer allowed. You may still override keys by setting "+
+						"`name = { key = value }`. The maps will be merged. This "+
+						"behavior appeared in 0.7.0.", name))
+				continue
+			}
+		}
+
 		schema, ok := cvs[name]
 		if !ok {
 			continue
diff --git a/terraform/semantics_test.go b/terraform/semantics_test.go
index f40f2af69..9a37decd9 100644
--- a/terraform/semantics_test.go
+++ b/terraform/semantics_test.go
@@ -24,7 +24,7 @@ func TestSMCUserVariables(t *testing.T) {
 		"foo":     "bar",
 		"map.foo": "baz",
 	})
-	if len(errs) != 0 {
+	if len(errs) == 0 {
 		t.Fatalf("err: %#v", errs)
 	}
 
diff --git a/terraform/test-fixtures/validate-var-map-override-old/main.tf b/terraform/test-fixtures/validate-var-map-override-old/main.tf
new file mode 100644
index 000000000..7fe646c8b
--- /dev/null
+++ b/terraform/test-fixtures/validate-var-map-override-old/main.tf
@@ -0,0 +1 @@
+variable "foo" { default = { foo = "bar" } }