diff --git a/notacceptable.go b/notacceptable.go
new file mode 100644
index 0000000..c274f6c
--- /dev/null
+++ b/notacceptable.go
@@ -0,0 +1,36 @@
+package httpaccept
+
+import (
+	"fmt"
+	"strings"
+)
+
+var _ error = &internalNotAcceptable{}
+
+type internalNotAcceptable struct {
+	mediatypes []string
+}
+
+func (receiver internalNotAcceptable) Error() string {
+	var mediatypes []string = receiver.mediatypes
+
+	if len(mediatypes) < 1 {
+		return "httpaccept: none of the provided media-types are acceptable, because an empty list of media-types was provided"
+	}
+
+	var buffer strings.Builder
+	buffer.WriteString("httpaccept: none of the provided media-types are acceptable —")
+	for _, mediatype := range mediatypes {
+		fmt.Fprintf(&buffer, " %q", mediatype)
+	}
+
+	return buffer.String()
+}
+
+func (internalNotAcceptable) ClientError() {
+	// Nothing here.
+}
+
+func (internalNotAcceptable) NotAcceptable() {
+	// Nothing here.
+}