diff --git a/dataext/syncSet.go b/dataext/syncSet.go
index fae5c82..31197fb 100644
--- a/dataext/syncSet.go
+++ b/dataext/syncSet.go
@@ -7,6 +7,9 @@ type SyncSet[TData comparable] struct {
 	lock sync.Mutex
 }
 
+// Add adds `value` to the set
+// returns true  if the value was actually inserted
+// returns false if the value already existed
 func (s *SyncSet[TData]) Add(value TData) bool {
 	s.lock.Lock()
 	defer s.lock.Unlock()
@@ -15,10 +18,10 @@ func (s *SyncSet[TData]) Add(value TData) bool {
 		s.data = make(map[TData]bool)
 	}
 
-	_, ok := s.data[value]
+	_, existsInPreState := s.data[value]
 	s.data[value] = true
 
-	return !ok
+	return !existsInPreState
 }
 
 func (s *SyncSet[TData]) AddAll(values []TData) {
diff --git a/exerr/data.go b/exerr/data.go
index e42135e..8f23340 100644
--- a/exerr/data.go
+++ b/exerr/data.go
@@ -1,6 +1,7 @@
 package exerr
 
 import (
+	"gogs.mikescher.com/BlackForestBytes/goext/dataext"
 	"gogs.mikescher.com/BlackForestBytes/goext/langext"
 )
 
@@ -37,25 +38,32 @@ type ErrorType struct {
 
 //goland:noinspection GoUnusedGlobalVariable
 var (
-	TypeInternal       = ErrorType{"INTERNAL_ERROR", langext.Ptr(500)}
-	TypePanic          = ErrorType{"PANIC", langext.Ptr(500)}
-	TypeNotImplemented = ErrorType{"NOT_IMPLEMENTED", langext.Ptr(500)}
+	TypeInternal       = NewType("INTERNAL_ERROR", langext.Ptr(500))
+	TypePanic          = NewType("PANIC", langext.Ptr(500))
+	TypeNotImplemented = NewType("NOT_IMPLEMENTED", langext.Ptr(500))
 
-	TypeWrap = ErrorType{"Wrap", nil}
+	TypeWrap = NewType("Wrap", nil)
 
-	TypeBindFailURI      = ErrorType{"BINDFAIL_URI", langext.Ptr(400)}
-	TypeBindFailQuery    = ErrorType{"BINDFAIL_QUERY", langext.Ptr(400)}
-	TypeBindFailJSON     = ErrorType{"BINDFAIL_JSON", langext.Ptr(400)}
-	TypeBindFailFormData = ErrorType{"BINDFAIL_FORMDATA", langext.Ptr(400)}
-	TypeBindFailHeader   = ErrorType{"BINDFAIL_HEADER", langext.Ptr(400)}
+	TypeBindFailURI      = NewType("BINDFAIL_URI", langext.Ptr(400))
+	TypeBindFailQuery    = NewType("BINDFAIL_QUERY", langext.Ptr(400))
+	TypeBindFailJSON     = NewType("BINDFAIL_JSON", langext.Ptr(400))
+	TypeBindFailFormData = NewType("BINDFAIL_FORMDATA", langext.Ptr(400))
+	TypeBindFailHeader   = NewType("BINDFAIL_HEADER", langext.Ptr(400))
 
-	TypeUnauthorized = ErrorType{"UNAUTHORIZED", langext.Ptr(401)}
-	TypeAuthFailed   = ErrorType{"AUTH_FAILED", langext.Ptr(401)}
+	TypeUnauthorized = NewType("UNAUTHORIZED", langext.Ptr(401))
+	TypeAuthFailed   = NewType("AUTH_FAILED", langext.Ptr(401))
 
 	// other values come from pkgconfig
 )
 
+var registeredTypes = dataext.SyncSet[string]{}
+
 func NewType(key string, defStatusCode *int) ErrorType {
+	insertOkay := registeredTypes.Add(key)
+	if !insertOkay {
+		panic("Cannot register same ErrType ('" + key + "') more than once")
+	}
+
 	return ErrorType{key, defStatusCode}
 }
 
diff --git a/goextVersion.go b/goextVersion.go
index ba3511a..1d43391 100644
--- a/goextVersion.go
+++ b/goextVersion.go
@@ -1,5 +1,5 @@
 package goext
 
-const GoextVersion = "0.0.226"
+const GoextVersion = "0.0.227"
 
-const GoextVersionTimestamp = "2023-08-08T14:28:09+0200"
+const GoextVersionTimestamp = "2023-08-08T15:28:29+0200"