diff --git a/sumpy/expansion/__init__.py b/sumpy/expansion/__init__.py
index 54dbfd75faa3b3995da30d79c3362bbaf9f52d14..480f53fcdd1efc7dba7562f96ebcd7d5dcbb804e 100644
--- a/sumpy/expansion/__init__.py
+++ b/sumpy/expansion/__init__.py
@@ -491,7 +491,7 @@ class LaplaceExpansionTermsWrangler(LinearRecurrenceBasedExpansionTermsWrangler)
             pde_dict[tuple(mi)] = 1
         return pde_dict
 
-    def get_reduced_coeffs(self, nullspace):
+    def _get_reduced_coeffs(self, nullspace):
         idx = []
         for i, mi in enumerate(self.get_full_coefficient_identifiers()):
             # Return only the derivatives with the order of the last dimension
@@ -521,7 +521,7 @@ class HelmholtzExpansionTermsWrangler(LinearRecurrenceBasedExpansionTermsWrangle
         pde_dict[tuple([0]*self.dim)] = 1
         return pde_dict
 
-    def get_reduced_coeffs(self, nullspace):
+    def _get_reduced_coeffs(self, nullspace):
         idx = []
         for i, mi in enumerate(self.get_full_coefficient_identifiers()):
             # Return only the derivatives with the order of the last dimension