diff --git a/src/ext/elphel/elphel_php.c b/src/ext/elphel/elphel_php.c
index 6771a9eced8eca075e96e50596e46c8dd8c450ac..ac9b1e10b0d3e352a83c8193f6bf28126dd02c47 100644
--- a/src/ext/elphel/elphel_php.c
+++ b/src/ext/elphel/elphel_php.c
@@ -2428,7 +2428,7 @@ PHP_FUNCTION(elphel_capture_range) {
 	long frame = 0;
 	long duration=0;
 	long this_frame = ELPHEL_GLOBALPARS(port, G_THIS_FRAME);
-	long maxahead = PARS_FRAMES_MASK - 3; // -2?
+	long maxahead = PARS_FRAMES_MASK - 4; // 3; // -2?
 	long ahead, frame_stop;
     if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "ll|ll", &port, &port_mask, &frame, &duration) == FAILURE)
         RETURN_NULL();