diff --git a/frappy_psi/ahcapbridge.py b/frappy_psi/ahcapbridge.py
index 36f51f3f..0a9ed9c2 100644
--- a/frappy_psi/ahcapbridge.py
+++ b/frappy_psi/ahcapbridge.py
@@ -81,7 +81,7 @@ class IO(StringIO):
 
 
 class AHBase(HasIO, Pinata, Acquisition):
-    value = Parameter('capacitance', FloatRange(unit='pF'))
+    value = Parameter('capacitance', FloatRange(unit='pF', fmtstr='%.8g'))
     freq = Parameter('frequency', FloatRange(unit='Hz'), default=1000)
     voltage = Parameter('upper voltage limit',
                         FloatRange(0, 15, unit='V', fmtstr='%.1f'),