diff --git a/ndstruct/src/coo/coo_error.rs b/ndstruct/src/coo/coo_error.rs
index 6333d10..709cb50 100644
--- a/ndstruct/src/coo/coo_error.rs
+++ b/ndstruct/src/coo/coo_error.rs
@@ -53,5 +53,4 @@ impl Display for CooError {
   }
 }
 
-#[cfg(feature = "std")]
-impl std::error::Error for CooError {}
+impl core::error::Error for CooError {}
diff --git a/ndstruct/src/csl/csl_error.rs b/ndstruct/src/csl/csl_error.rs
index ccdcedc..9af1e38 100644
--- a/ndstruct/src/csl/csl_error.rs
+++ b/ndstruct/src/csl/csl_error.rs
@@ -120,5 +120,4 @@ impl Display for CslError {
   }
 }
 
-#[cfg(feature = "std")]
-impl std::error::Error for CslError {}
+impl core::error::Error for CslError {}
diff --git a/ndstruct/src/csl/csl_line_constructor.rs b/ndstruct/src/csl/csl_line_constructor.rs
index 4c96ce0..26630d7 100644
--- a/ndstruct/src/csl/csl_line_constructor.rs
+++ b/ndstruct/src/csl/csl_line_constructor.rs
@@ -170,5 +170,4 @@ impl Display for CslLineConstructorError {
   }
 }
 
-#[cfg(feature = "std")]
-impl std::error::Error for CslLineConstructorError {}
+impl core::error::Error for CslLineConstructorError {}
diff --git a/ndstruct/src/dense/dense_error.rs b/ndstruct/src/dense/dense_error.rs
index 20fa00c..c456dda 100644
--- a/ndstruct/src/dense/dense_error.rs
+++ b/ndstruct/src/dense/dense_error.rs
@@ -21,5 +21,4 @@ impl Display for DenseError {
   }
 }
 
-#[cfg(feature = "std")]
-impl std::error::Error for DenseError {}
+impl core::error::Error for DenseError {}
diff --git a/ndstruct/src/error.rs b/ndstruct/src/error.rs
index 954c7fe..1ca8fa0 100644
--- a/ndstruct/src/error.rs
+++ b/ndstruct/src/error.rs
@@ -32,8 +32,7 @@ impl Display for Error {
   }
 }
 
-#[cfg(feature = "std")]
-impl std::error::Error for Error {}
+impl core::error::Error for Error {}
 
 impl From<cl_aux::Error> for Error {
   #[inline]