diff --git a/artiq/gui/explorer.py b/artiq/gui/explorer.py
index c8925256b..bed58ae39 100644
--- a/artiq/gui/explorer.py
+++ b/artiq/gui/explorer.py
@@ -75,8 +75,7 @@ class _NumberEntry(QtGui.QDoubleSpinBox):
     def __init__(self, procdesc):
         QtGui.QDoubleSpinBox.__init__(self)
         self.setDecimals(procdesc["ndecimals"])
-        if procdesc["step"] is not None:
-            self.setSingleStep(procdesc["step"])
+        self.setSingleStep(procdesc["step"])
         if procdesc["min"] is not None:
             self.setMinimum(procdesc["min"])
         else:
diff --git a/artiq/gui/scan.py b/artiq/gui/scan.py
index f3405200b..0065b421d 100644
--- a/artiq/gui/scan.py
+++ b/artiq/gui/scan.py
@@ -76,8 +76,7 @@ class ScanController(LayoutWidget):
             self.v_noscan.setMaximum(gmax)
         else:
             self.v_noscan.setMaximum(float("inf"))
-        if gstep is not None:
-            self.v_noscan.setSingleStep(gstep)
+        self.v_noscan.setSingleStep(gstep)
         if unit:
             self.v_noscan.setSuffix(" " + unit)
         self.v_noscan_gr = LayoutWidget()
diff --git a/artiq/language/environment.py b/artiq/language/environment.py
index fa3f30849..6a15118ba 100644
--- a/artiq/language/environment.py
+++ b/artiq/language/environment.py
@@ -79,7 +79,7 @@ class NumberValue(_SimpleArgProcessor):
     :param max: The maximum value of the argument.
     :param ndecimals: The number of decimals a UI should use.
     """
-    def __init__(self, default=NoDefault, unit="", step=None,
+    def __init__(self, default=NoDefault, unit="", step=1.0,
                  min=None, max=None, ndecimals=2):
         _SimpleArgProcessor.__init__(self, default)
         self.unit = unit
diff --git a/artiq/language/scan.py b/artiq/language/scan.py
index fe22c5a4f..17352b829 100644
--- a/artiq/language/scan.py
+++ b/artiq/language/scan.py
@@ -121,7 +121,7 @@ class Scannable:
     :param ndecimals: The number of decimals a UI should use.
     """
     def __init__(self, default=NoDefault, unit="",
-                 global_step=None, global_min=None, global_max=None,
+                 global_step=1.0, global_min=None, global_max=None,
                  ndecimals=2):
         if default is not NoDefault:
             self.default_value = default