diff --git a/src/bin/libint/dg.cc b/src/bin/libint/dg.cc
index cdb384388..8bc82153d 100644
--- a/src/bin/libint/dg.cc
+++ b/src/bin/libint/dg.cc
@@ -2331,7 +2331,7 @@ namespace libint2 {
   namespace {
 #if USE_ASSOCCONTAINER_BASED_DIRECTEDGRAPH
     typedef DirectedGraph::targets::value_type value_type;
-    struct __NotUnrolledIntegralSet : public std::unary_function<const value_type&,bool> {
+    struct __NotUnrolledIntegralSet {
       bool operator()(const value_type& v) {
         return NotUnrolledIntegralSet()(v);
       }
diff --git a/src/bin/libint/dgvertex.h b/src/bin/libint/dgvertex.h
index 76d0bba13..f20ba286a 100644
--- a/src/bin/libint/dgvertex.h
+++ b/src/bin/libint/dgvertex.h
@@ -305,15 +305,15 @@ namespace libint2 {
   // Nonmember predicates
   //
   /// return true if V is an unrolled IntegralSet
-  struct UnrolledIntegralSet : public std::unary_function<const SafePtr<DGVertex>&,bool> {
+  struct UnrolledIntegralSet {
     bool operator()(const SafePtr<DGVertex>& V);
   };
   /// return false if V is an unrolled IntegralSet
-  struct NotUnrolledIntegralSet : public std::unary_function<const SafePtr<DGVertex>&,bool> {
+  struct NotUnrolledIntegralSet {
     bool operator()(const SafePtr<DGVertex>& V);
   };
   /// return true if V is an Integral in an unrolled target IntegralSet
-  struct IntegralInTargetIntegralSet : public std::unary_function<const SafePtr<DGVertex>&,bool> {
+  struct IntegralInTargetIntegralSet {
     bool operator()(const SafePtr<DGVertex>& V);
   };
 
diff --git a/src/bin/libint/uncontract.h b/src/bin/libint/uncontract.h
index f5e58289b..385a71d14 100644
--- a/src/bin/libint/uncontract.h
+++ b/src/bin/libint/uncontract.h
@@ -192,7 +192,7 @@ namespace libint2 {
   }
 
   /// return true if V is a decontracted IntegralSet
-  struct DecontractedIntegralSet : public std::unary_function<const SafePtr<DGVertex>&,bool> {
+  struct DecontractedIntegralSet {
     bool operator()(const SafePtr<DGVertex>& V) {
       const unsigned int outdegree = V->num_exit_arcs();
       if (outdegree == 0) return false;