diff --git a/backend/hdf5/DimensionHDF5.cpp b/backend/hdf5/DimensionHDF5.cpp
index e96d9eb2..278f9b0b 100644
--- a/backend/hdf5/DimensionHDF5.cpp
+++ b/backend/hdf5/DimensionHDF5.cpp
@@ -249,8 +249,8 @@ DimensionType SetDimensionHDF5::dimensionType() const {
 }
 
 
-boost::optional<std::string> SetDimensionHDF5::label() const {
-    boost::optional<std::string> ret;
+std::optional<std::string> SetDimensionHDF5::label() const {
+    std::optional<std::string> ret;
     string label;
     bool have_attr = group.getAttr("label", label);
     if (have_attr) {
diff --git a/backend/hdf5/DimensionHDF5.hpp b/backend/hdf5/DimensionHDF5.hpp
index feb4c0c5..ba0b8cb8 100644
--- a/backend/hdf5/DimensionHDF5.hpp
+++ b/backend/hdf5/DimensionHDF5.hpp
@@ -127,7 +127,7 @@ class SetDimensionHDF5 : virtual public base::ISetDimension, public DimensionHDF
     DimensionType dimensionType() const;
 
 
-    boost::optional<std::string> label() const;
+    std::optional<std::string> label() const;
 
     
     void label(const std::string &label);
diff --git a/include/nix/Dimensions.hpp b/include/nix/Dimensions.hpp
index c8bfa668..2e36aad3 100644
--- a/include/nix/Dimensions.hpp
+++ b/include/nix/Dimensions.hpp
@@ -783,7 +783,7 @@ class NIXAPI SetDimension : public base::ImplContainer<base::ISetDimension> {
      *
      * @return The label of the dimension.
      */
-    boost::optional<std::string> label() const {
+    std::optional<std::string> label() const {
         return backend()->label();
     }
 
diff --git a/include/nix/base/IDimensions.hpp b/include/nix/base/IDimensions.hpp
index b3e34fb7..f58e5476 100644
--- a/include/nix/base/IDimensions.hpp
+++ b/include/nix/base/IDimensions.hpp
@@ -139,7 +139,7 @@ class NIXAPI ISetDimension : virtual public IDimension {
 
 public:
 
-    virtual boost::optional<std::string> label() const = 0;
+    virtual std::optional<std::string> label() const = 0;
 
     virtual void label(const std::string &label) = 0;