diff --git a/ohmpi/hardware_components/ohmpi_card_3_15.py b/ohmpi/hardware_components/ohmpi_card_3_15.py
index f4aa3b080fd68ee872bae8957a637c29059c353d..fc7bf94a73e059640c4b0a16700ef9cccb0545a1 100644
--- a/ohmpi/hardware_components/ohmpi_card_3_15.py
+++ b/ohmpi/hardware_components/ohmpi_card_3_15.py
@@ -149,7 +149,7 @@ class Tx(TxAbstract):
 
     def inject(self, polarity=1, inj_time=None):
         self.polarity = polarity
-        TxAbstract.inject(self, polarity=polarity, inj_time=None)
+        TxAbstract.inject(self, polarity=polarity, inj_time=inj_time)
 
     @property
     def polarity(self):