diff --git a/helper/schema/schema.go b/helper/schema/schema.go
index 558871ddb..0a79e1281 100644
--- a/helper/schema/schema.go
+++ b/helper/schema/schema.go
@@ -136,6 +136,8 @@ type Schema struct {
 	// logic. It is yielded the provided config value as an interface{} that is
 	// guaranteed to be of the proper Schema type, and it can yield warnings or
 	// errors based on inspection of that value.
+	//
+	// ValidateFunc currently only works for primitive types.
 	ValidateFunc SchemaValidateFunc
 }
 
@@ -513,6 +515,13 @@ func (m schemaMap) InternalValidate(topSchemaMap schemaMap) error {
 				}
 			}
 		}
+
+		if v.ValidateFunc != nil {
+			switch v.Type {
+			case TypeList, TypeSet, TypeMap:
+				return fmt.Errorf("ValidateFunc is only supported on primitives.")
+			}
+		}
 	}
 
 	return nil
@@ -1128,6 +1137,7 @@ func (m schemaMap) validatePrimitive(
 		return nil, nil
 	}
 
+	var decoded interface{}
 	switch schema.Type {
 	case TypeBool:
 		// Verify that we can parse this as the correct type
@@ -1135,28 +1145,36 @@ func (m schemaMap) validatePrimitive(
 		if err := mapstructure.WeakDecode(raw, &n); err != nil {
 			return nil, []error{err}
 		}
+		decoded = n
 	case TypeInt:
 		// Verify that we can parse this as an int
 		var n int
 		if err := mapstructure.WeakDecode(raw, &n); err != nil {
 			return nil, []error{err}
 		}
+		decoded = n
 	case TypeFloat:
 		// Verify that we can parse this as an int
 		var n float64
 		if err := mapstructure.WeakDecode(raw, &n); err != nil {
 			return nil, []error{err}
 		}
+		decoded = n
 	case TypeString:
 		// Verify that we can parse this as a string
 		var n string
 		if err := mapstructure.WeakDecode(raw, &n); err != nil {
 			return nil, []error{err}
 		}
+		decoded = n
 	default:
 		panic(fmt.Sprintf("Unknown validation type: %#v", schema.Type))
 	}
 
+	if schema.ValidateFunc != nil {
+		return schema.ValidateFunc(decoded)
+	}
+
 	return nil, nil
 }
 
@@ -1186,16 +1204,6 @@ func (m schemaMap) validateType(
 			"%q: [REMOVED] %s", k, schema.Removed))
 	}
 
-	if len(es) == 0 && schema.ValidateFunc != nil {
-		ws2, es2 := schema.ValidateFunc(raw)
-		for _, w := range ws2 {
-			ws = append(ws, fmt.Sprintf("%q: %s", k, w))
-		}
-		for _, e := range es2 {
-			es = append(es, fmt.Errorf("%q: %s", k, e))
-		}
-	}
-
 	return ws, es
 }
 
diff --git a/helper/schema/schema_test.go b/helper/schema/schema_test.go
index 36aa2e137..5ea108380 100644
--- a/helper/schema/schema_test.go
+++ b/helper/schema/schema_test.go
@@ -2796,6 +2796,20 @@ func TestSchemaMap_InternalValidate(t *testing.T) {
 			},
 			false,
 		},
+
+		// ValidateFunc on non-primitive
+		{
+			map[string]*Schema{
+				"foo": &Schema{
+					Type:     TypeMap,
+					Required: true,
+					ValidateFunc: func(v interface{}) (ws []string, es []error) {
+						return
+					},
+				},
+			},
+			true,
+		},
 	}
 
 	for i, tc := range cases {
@@ -3435,7 +3449,7 @@ func TestSchemaMap_Validate(t *testing.T) {
 			},
 			Err: true,
 			Errors: []error{
-				fmt.Errorf(`"validate_me": something is not right here`),
+				fmt.Errorf(`something is not right here`),
 			},
 		},
 
@@ -3455,6 +3469,23 @@ func TestSchemaMap_Validate(t *testing.T) {
 			},
 			Err: true,
 		},
+		"ValidateFunc gets decoded type": {
+			Schema: map[string]*Schema{
+				"maybe": &Schema{
+					Type:     TypeBool,
+					Required: true,
+					ValidateFunc: func(v interface{}) (ws []string, es []error) {
+						if _, ok := v.(bool); !ok {
+							t.Fatalf("Expected bool, got: %#v", v)
+						}
+						return
+					},
+				},
+			},
+			Config: map[string]interface{}{
+				"maybe": "true",
+			},
+		},
 	}
 
 	for tn, tc := range cases {