diff --git a/include/sirit/sirit.h b/include/sirit/sirit.h
index eded07e..4119a5f 100644
--- a/include/sirit/sirit.h
+++ b/include/sirit/sirit.h
@@ -11,6 +11,7 @@
 #include <optional>
 #include <set>
 #include <spirv/unified1/spirv.hpp11>
+#include <string>
 #include <variant>
 #include <vector>
 
@@ -38,6 +39,9 @@ class Module {
      */
     std::vector<std::uint8_t> Assemble() const;
 
+    /// Adds a SPIR-V extension.
+    void AddExtension(const std::string& extension_name);
+
     /// Adds a module capability.
     void AddCapability(spv::Capability capability);
 
@@ -620,6 +624,7 @@ class Module {
 
     std::uint32_t bound{1};
 
+    std::set<std::string> extensions;
     std::set<spv::Capability> capabilities;
     std::unique_ptr<Op> glsl_std_450;
     std::set<std::unique_ptr<Op>> ext_inst_import;
diff --git a/src/sirit.cpp b/src/sirit.cpp
index e03fcdf..9112a80 100644
--- a/src/sirit.cpp
+++ b/src/sirit.cpp
@@ -38,10 +38,16 @@ std::vector<u8> Module::Assemble() const {
         op.Add(static_cast<u32>(capability));
         op.Write(stream);
     }
+
+    for (const auto& extension_name : extensions) {
+        Op op(spv::Op::OpExtension);
+        op.Add(extension_name);
+        op.Write(stream);
+    }
+
     if (glsl_std_450) {
         glsl_std_450->Write(stream);
     }
-    // TODO write ext inst imports
 
     Op memory_model_ref{spv::Op::OpMemoryModel};
     memory_model_ref.Add(static_cast<u32>(addressing_model));
@@ -59,6 +65,10 @@ std::vector<u8> Module::Assemble() const {
     return bytes;
 }
 
+void Module::AddExtension(const std::string& extension_name) {
+    extensions.insert(extension_name);
+}
+
 void Module::AddCapability(spv::Capability capability) {
     capabilities.insert(capability);
 }