diff --git a/histbook/hist.py b/histbook/hist.py
index f7ec660..dbe858b 100644
--- a/histbook/hist.py
+++ b/histbook/hist.py
@@ -107,6 +107,8 @@ def recurse(node):
     def _fill(self, arrays):
         self.fields  # for the side-effect of creating self._instructions
 
+        maybeconstants = {"pi": numpy.pi, "Pi": numpy.pi, "e": numpy.e, "E": numpy.e, "inf": numpy.inf, "Inf": numpy.inf, "infinity": numpy.inf, "Infinity": numpy.inf, "nan": numpy.nan, "NaN": numpy.nan, "Nan": numpy.nan}
+
         length = None
         firstinstruction = None
         firstarray = None
@@ -115,7 +117,10 @@ def _fill(self, arrays):
                 try:
                     array = arrays[instruction.extern.value]
                 except KeyError:
-                    raise ValueError("required field {0} not found in fill arguments".format(repr(str(instruction.extern))))
+                    if instruction.extern.value in maybeconstants:
+                        continue
+                    else:
+                        raise ValueError("required field {0} not found in fill arguments".format(repr(str(instruction.extern))))
 
                 if not isinstance(array, numpy.ndarray):
                     array = numpy.array(array)
@@ -139,7 +144,10 @@ def _fill(self, arrays):
                     try:
                         array = arrays[instruction.extern.value]
                     except KeyError:
-                        raise ValueError("required field {0} not found in fill arguments".format(repr(str(instruction.extern))))
+                        if instruction.extern.value in maybeconstants:
+                            array = numpy.full(length, maybeconstants[instruction.extern.value])
+                        else:
+                            raise ValueError("required field {0} not found in fill arguments".format(repr(str(instruction.extern))))
 
                 if not isinstance(array, numpy.ndarray):
                     array = numpy.array(array)