diff --git a/include/klay/circuit.h b/include/klay/circuit.h
index 784ada0..8e9ca03 100644
--- a/include/klay/circuit.h
+++ b/include/klay/circuit.h
@@ -10,6 +10,8 @@
 #include "node.h"
 #include "hash_set8.hpp"
 
+namespace klay {
+
 class NodePtr {
 public:
     NodePtr(Node* ptr) : ptr(ptr) { }
@@ -216,3 +218,5 @@ class Circuit {
         return NodePtr(add_node_level_compressed(node));
     }
 };
+
+}  // namespace klay
diff --git a/include/klay/indices.h b/include/klay/indices.h
index a0e62e2..470fd07 100644
--- a/include/klay/indices.h
+++ b/include/klay/indices.h
@@ -12,6 +12,7 @@
 
 namespace nb = nanobind;
 using namespace nb::literals;
+using namespace klay;
 
 using Array = nb::ndarray<nb::numpy, long int, nb::shape<-1>>;
 using Arrays = std::vector<Array>;
diff --git a/include/klay/literal.h b/include/klay/literal.h
index cfa5b99..d4ac0c3 100644
--- a/include/klay/literal.h
+++ b/include/klay/literal.h
@@ -3,6 +3,8 @@
 #include <iostream>
 using namespace std;
 
+namespace klay {
+
 typedef int Var;
 
 /**
@@ -65,4 +67,6 @@ class Lit {
 
 Lit Lit::fromInt(int i) {
     return Lit(std::abs(i), i < 0);
-}
\ No newline at end of file
+}
+
+}  // namespace klay
diff --git a/include/klay/node.h b/include/klay/node.h
index 87bcb15..b1cc937 100644
--- a/include/klay/node.h
+++ b/include/klay/node.h
@@ -10,6 +10,8 @@
 
 #include "cassert"
 
+namespace klay {
+
 enum class NodeType {True, False, Or, And, Leaf};
 
 
@@ -127,3 +129,4 @@ struct NodeEqual {
 };
 
 
+}  // namespace klay
diff --git a/src/circuit.cpp b/src/circuit.cpp
index fe46a49..e3cebad 100644
--- a/src/circuit.cpp
+++ b/src/circuit.cpp
@@ -1,6 +1,8 @@
 #include "klay/circuit.h"
 #include "cassert"
 
+using namespace klay;
+
 Node* Circuit::add_node(Node* node) {
     if (layers.size() <= node->layer)
         layers.resize(node->layer + 1);
diff --git a/src/indices.cpp b/src/indices.cpp
index 16bc18d..0d8ca59 100644
--- a/src/indices.cpp
+++ b/src/indices.cpp
@@ -1,6 +1,8 @@
 #include <klay/indices.h>
 #include <klay/circuit.h>
 
+using namespace klay;
+
 void cleanup(void* data) noexcept {
   delete[] static_cast<long int*>(data);
 }
diff --git a/src/klay_bindings.cpp b/src/klay_bindings.cpp
index 532621e..305f586 100644
--- a/src/klay_bindings.cpp
+++ b/src/klay_bindings.cpp
@@ -8,6 +8,7 @@
 #include "klay/circuit.h"
 #include "klay/indices.h"
 
+using namespace klay;
 namespace nb = nanobind;
 using namespace nb::literals;
 
diff --git a/src/node.cpp b/src/node.cpp
index 31e60cd..7f68d61 100644
--- a/src/node.cpp
+++ b/src/node.cpp
@@ -1,5 +1,7 @@
 #include "klay/node.h"
 
+using namespace klay;
+
 /**
  * Improve bit dispersion of a given hash value h.
  */