diff --git a/pymbolic/compiler.py b/pymbolic/compiler.py
index c652d52fdcdd4bf14849c3d78ace8dc8676698db..96ff2c9a347800cfdbbfb823be1eb747853b55f4 100644
--- a/pymbolic/compiler.py
+++ b/pymbolic/compiler.py
@@ -29,26 +29,21 @@ from pymbolic.mapper.stringifier import (StringifyMapper, PREC_NONE,
         PREC_SUM, PREC_POWER)
 
 
-def _constant_mapper(c):
-    # work around numpy bug #1137 (locale-sensitive repr)
-    # http://projects.scipy.org/numpy/ticket/1137
-    try:
-        import numpy
-    except ImportError:
-        pass
-    else:
-        if isinstance(c, numpy.floating):
-            c = float(c)
-        elif isinstance(c, numpy.complexfloating):
-            c = complex(c)
-
-    return repr(c)
-
-
 class CompileMapper(StringifyMapper):
-    def __init__(self):
-        StringifyMapper.__init__(self,
-                constant_mapper=_constant_mapper)
+    def map_constant(self, expr, enclosing_prec):
+        # work around numpy bug #1137 (locale-sensitive repr)
+        # http://projects.scipy.org/numpy/ticket/1137
+        try:
+            import numpy
+        except ImportError:
+            pass
+        else:
+            if isinstance(expr, numpy.floating):
+                expr = float(expr)
+            elif isinstance(expr, numpy.complexfloating):
+                expr = complex(expr)
+
+        return repr(expr)
 
     def map_polynomial(self, expr, enclosing_prec):
         # Use Horner's scheme to evaluate the polynomial
diff --git a/pymbolic/mapper/stringifier.py b/pymbolic/mapper/stringifier.py
index f1afc0f8d31494176e97b215c73fb9e8d6366152..79fd743bce772323c078a7793353fe160b8214f5 100644
--- a/pymbolic/mapper/stringifier.py
+++ b/pymbolic/mapper/stringifier.py
@@ -95,7 +95,7 @@ class StringifyMapper(pymbolic.mapper.Mapper):
                     "achieve the desired effect. "
                     "The 'constant_mapper' argument will "
                     "disappear after June 2020.",
-                    DeprecationWarning)
+                    DeprecationWarning, stacklevel=2)
 
         self.constant_mapper = constant_mapper