diff --git a/src/collected_substring.rs b/src/collected_substring.rs
index 59eee9c..a97b790 100644
--- a/src/collected_substring.rs
+++ b/src/collected_substring.rs
@@ -12,7 +12,7 @@ pub trait Keyword<C: Copy> {
     ) -> Option<impl KeywordComparatorIterator<C> + use<'keyword, Self, C>>;
 }
 
-pub trait CollectedSubstring {
+pub trait CollectedSubstring: Sized {
     type C: Copy;
     fn compareKeyword(&self, kw: impl Keyword<Self::C>) -> bool;
 }
diff --git a/src/converter/converters.rs b/src/converter/converters.rs
index 71e9cfd..aef80b1 100644
--- a/src/converter/converters.rs
+++ b/src/converter/converters.rs
@@ -19,7 +19,7 @@ pub trait StreamConverter_Substring<C: Copy, CS: CollectedSubstring<C = C>>:
 }
 
 pub trait StreamConverter<C: Copy, P: Pos, CS: CollectedSubstring<C = C>>:
-    StreamConverter_Char<C> + StreamConverter_Pos<P> + StreamConverter_Substring<C, CS>
+    Sized + StreamConverter_Char<C> + StreamConverter_Pos<P> + StreamConverter_Substring<C, CS>
 {
 }
 
@@ -27,7 +27,7 @@ impl<
     C: Copy,
     P: Pos,
     CS: CollectedSubstring<C = C>,
-    W: StreamConverter_Char<C> + StreamConverter_Pos<P> + StreamConverter_Substring<C, CS>,
+    W: Sized + StreamConverter_Char<C> + StreamConverter_Pos<P> + StreamConverter_Substring<C, CS>,
 > StreamConverter<C, P, CS> for W
 {
 }
diff --git a/src/pos/pos.rs b/src/pos/pos.rs
index ad8ef90..7752a59 100644
--- a/src/pos/pos.rs
+++ b/src/pos/pos.rs
@@ -1,4 +1,4 @@
-pub trait Pos {}
+pub trait Pos: Sized {}
 
 impl Pos for () {}
-impl Pos for usize {}
\ No newline at end of file
+impl Pos for usize {}
diff --git a/src/pos/pos_counter.rs b/src/pos/pos_counter.rs
index 755f9af..0e27806 100644
--- a/src/pos/pos_counter.rs
+++ b/src/pos/pos_counter.rs
@@ -1,9 +1,9 @@
 use crate::pos::Pos;
 
-pub trait PosCounter<C: Copy> {
+pub trait PosCounter<C: Copy>: Sized {
     type P: Pos;
 
     fn update(&mut self, c: C);
 
     fn export(&self) -> Self::P;
-}
\ No newline at end of file
+}