diff --git a/src/constraint/alldifferent.rs b/src/constraint/alldifferent.rs
index c01546a..624dc71 100644
--- a/src/constraint/alldifferent.rs
+++ b/src/constraint/alldifferent.rs
@@ -37,7 +37,7 @@ impl Constraint for AllDifferent {
         Box::new(self.vars.iter())
     }
 
-    fn on_assigned(&self, search: &mut PuzzleSearch, var: VarToken, val: Val) -> PsResult<()> {
+    fn propagate(&self, search: &mut PuzzleSearch, var: VarToken, val: Val) -> PsResult<()> {
         for &var2 in self.vars.iter().filter(|&v| *v != var) {
             search.remove_candidate(var2, val)?;
         }
diff --git a/src/constraint/equality.rs b/src/constraint/equality.rs
index 557d5e1..8e66676 100644
--- a/src/constraint/equality.rs
+++ b/src/constraint/equality.rs
@@ -35,7 +35,7 @@ impl Constraint for Equality {
         Box::new(self.eqn.coef.keys())
     }
 
-    fn on_assigned(&self, search: &mut PuzzleSearch, _var: VarToken, _val: Val) -> PsResult<()> {
+    fn propagate(&self, search: &mut PuzzleSearch, _var: VarToken, _val: Val) -> PsResult<()> {
         let mut sum = self.eqn.constant;
         let mut unassigned_var = None;
 
diff --git a/src/constraint/mod.rs b/src/constraint/mod.rs
index 0e2ec81..74a733d 100644
--- a/src/constraint/mod.rs
+++ b/src/constraint/mod.rs
@@ -16,9 +16,7 @@ pub trait Constraint: Debug {
     fn vars(&self) -> Box<dyn Iterator<Item = &'_ VarToken> + '_>;
 
     /// Applied after a variable has been assigned.
-    fn on_assigned(&self, _search: &mut PuzzleSearch, _var: VarToken, _val: Val) -> PsResult<()> {
-        Ok(())
-    }
+    fn propagate(&self, _search: &mut PuzzleSearch, _var: VarToken, _val: Val) -> PsResult<()>; 
 
     /// Applied after a variable's candidates has been modified.
     fn on_updated(&self, _search: &mut PuzzleSearch) -> PsResult<()> {
diff --git a/src/constraint/unify.rs b/src/constraint/unify.rs
index 2402ad3..9012b72 100644
--- a/src/constraint/unify.rs
+++ b/src/constraint/unify.rs
@@ -3,7 +3,7 @@
 use std::iter;
 use std::rc::Rc;
 
-use crate::{Constraint, PsResult, PuzzleSearch, VarToken};
+use crate::{Constraint, PsResult, PuzzleSearch, Val, VarToken};
 
 #[derive(Debug)]
 pub struct Unify {
@@ -39,6 +39,10 @@ impl Constraint for Unify {
         }
     }
 
+    fn propagate(&self, _search: &mut PuzzleSearch, _var: VarToken, _val: Val) -> PsResult<()> {
+        Ok(())
+    }
+
     fn on_updated(&self, search: &mut PuzzleSearch) -> PsResult<()> {
         if self.var1 != self.var2 {
             search.unify(self.var1, self.var2)
diff --git a/src/puzzle.rs b/src/puzzle.rs
index c4a1dd1..75143b9 100644
--- a/src/puzzle.rs
+++ b/src/puzzle.rs
@@ -857,7 +857,7 @@ impl<'a> PuzzleSearch<'a> {
         for cidx in 0..self.constraints.constraints.len() {
             if self.constraints.wake[idx].contains(cidx) {
                 let constraint = self.constraints.constraints[cidx].clone();
-                constraint.on_assigned(self, var, val)?;
+                constraint.propagate(self, var, val)?;
             }
         }
 
diff --git a/tests/queens.rs b/tests/queens.rs
index 0bc5ef9..317a264 100644
--- a/tests/queens.rs
+++ b/tests/queens.rs
@@ -17,7 +17,7 @@ impl Constraint for NoDiagonal {
         Box::new(self.vars.iter())
     }
 
-    fn on_assigned(&self, search: &mut PuzzleSearch, var: VarToken, val: Val) -> PsResult<()> {
+    fn propagate(&self, search: &mut PuzzleSearch, var: VarToken, val: Val) -> PsResult<()> {
         let y1 = self
             .vars
             .iter()
diff --git a/tests/takuzu.rs b/tests/takuzu.rs
index 5c9544a..2c11ad9 100644
--- a/tests/takuzu.rs
+++ b/tests/takuzu.rs
@@ -23,7 +23,7 @@ impl Constraint for BinaryRepr {
         Box::new(iter::once(&self.value).chain(&self.bits))
     }
 
-    fn on_assigned(&self, search: &mut PuzzleSearch, var: VarToken, val: Val) -> PsResult<()> {
+    fn propagate(&self, search: &mut PuzzleSearch, var: VarToken, val: Val) -> PsResult<()> {
         if var == self.value {
             let mut val = val;
             for &var in self.bits.iter() {