diff --git a/src/connection.c b/src/connection.c
index 2ca9bcee..9bb850cb 100644
--- a/src/connection.c
+++ b/src/connection.c
@@ -419,6 +419,7 @@ get_next_argument(const char *signature, struct argument_details *details)
 			details->nullable = 1;
 		}
 	}
+	details->type = '\0';
 	return signature;
 }