diff --git a/src/mapper/collector.py b/src/mapper/collector.py
index 2dfc8d554846db139523b8b4e7798e47945899eb..bc1bc5344adb16082441b92e417fa32e8c6457d1 100644
--- a/src/mapper/collector.py
+++ b/src/mapper/collector.py
@@ -78,3 +78,11 @@ class TermCollector(IdentityMapper):
         result = pymbolic.flattened_sum(coeff*rep2term(termrep) 
                 for termrep, coeff in term2coeff.iteritems())
         return result
+
+    def handle_unsupported_expression(self, expr):
+        from pymbolic.primitives import AlgebraicLeaf
+        if isinstance(expr, AlgebraicLeaf):
+            return expr
+        else:
+            IdentityMapper.handle_unsupported_expression(self, expr)
+