Support proto3.
diff --git a/proto/text_parser.go b/proto/text_parser.go
index 4885bd7..f733f30 100644
--- a/proto/text_parser.go
+++ b/proto/text_parser.go
@@ -409,6 +409,10 @@
 				if typ.Elem().Kind() != reflect.Ptr {
 					break
 				}
+			} else if typ.Kind() == reflect.String {
+				// The proto3 exception is for a string field,
+				// which requires a colon.
+				break
 			}
 			needColon = false
 		}