1 files changed, 3 insertions, 1 deletions

diff --git a/vendor/github.com/hashicorp/terraform/helper/schema/field_reader_diff.go b/vendor/github.com/hashicorp/terraform/helper/schema/field_reader_diff.go
index ae35b4a..3e70acf 100644
--- a/vendor/github.com/hashicorp/terraform/helper/schema/field_reader_diff.go
+++ b/vendor/github.com/hashicorp/terraform/helper/schema/field_reader_diff.go
@@ -95,7 +95,9 @@ func (r *DiffFieldReader) readMap(
                 return FieldReadResult{}, err
         }
         if source.Exists {
-                result = source.Value.(map[string]interface{})
+                // readMap may return a nil value, or an unknown value placeholder in
+                // some cases, causing the type assertion to panic if we don't assign the ok value
+                result, _ = source.Value.(map[string]interface{})
                 resultSet = true
         }