diff --git a/fipy/terms/implicitSourceTerm.py b/fipy/terms/implicitSourceTerm.py
index f45e1c48c7..2e515dc956 100644
--- a/fipy/terms/implicitSourceTerm.py
+++ b/fipy/terms/implicitSourceTerm.py
@@ -20,6 +20,19 @@ class ImplicitSourceTerm(SourceTerm):
     where :math:`S` is the `coeff` value.
     """
 
+    def __init__(self, coeff=1., var=None):
+        r"""
+        Parameters
+        ----------
+        coeff : float or ~fipy.variables.cellVariable.CellVariable
+            Proportionality coefficient :math:`S` (default: 1)
+        var : ~fipy.variables.cellVariable.CellVariable
+            Variable :math:`\phi` that
+            :class:`~fipy.terms.implicitSourceTerm.ImplicitSourceTerm` is
+            implicit in.
+        """
+        super(ImplicitSourceTerm, self).__init__(coeff=coeff, var=var)
+
     def _getWeight(self, var, transientGeomCoeff=None, diffusionGeomCoeff=None):
         """
         Test for a bug due to the sign operator not being updating
diff --git a/fipy/terms/sourceTerm.py b/fipy/terms/sourceTerm.py
index 53b4bd77fd..4b10cb1112 100644
--- a/fipy/terms/sourceTerm.py
+++ b/fipy/terms/sourceTerm.py
@@ -15,9 +15,18 @@ class SourceTerm(CellTerm):
     .. attention:: This class is abstract. Always create one of its subclasses.
     """
     def __init__(self, coeff=0., var=None):
+        r"""
+        Parameters
+        ----------
+        coeff : float or ~fipy.variables.cellVariable.CellVariable
+            Coefficient of source (default: 0)
+        var : ~fipy.variables.cellVariable.CellVariable
+            Variable :math:`\phi` that
+            :class:`~fipy.terms.sourceTerm.SourceTerm` is implicit in.
+        """
         if self.__class__ is SourceTerm:
             raise AbstractBaseClassError
-        CellTerm.__init__(self, coeff=coeff, var=var)
+        super(SourceTerm, self).__init__(coeff=coeff, var=var)
 
     def _calcGeomCoeff(self, var):
         self._checkCoeff(var)