diff --git a/src/simd/_gen/unify/trace.go b/src/simd/_gen/unify/trace.go
index b0aa35255e4..d28e9b6f879 100644
--- a/src/simd/_gen/unify/trace.go
+++ b/src/simd/_gen/unify/trace.go
@@ -132,10 +132,12 @@ func (t *tracer) traceUnify(v, w *Value, e envSet) {
 		return
 	}
 
+	t.enc.e = e // Interpret values w.r.t. e
 	t.logf("Unify\n%s\nwith\n%s\nin\n%s",
 		yamlf("  ", t.enc.value(v)),
 		yamlf("  ", t.enc.value(w)),
 		yamlf("  ", t.enc.env(e)))
+	t.enc.e = envSet{}
 
 	if t.saveTree {
 		if t.node == nil {
diff --git a/src/simd/_gen/unify/yaml.go b/src/simd/_gen/unify/yaml.go
index dadcd71dd7b..a7a1d986e4c 100644
--- a/src/simd/_gen/unify/yaml.go
+++ b/src/simd/_gen/unify/yaml.go
@@ -316,6 +316,9 @@ func (dec *yamlDecoder) value(node *yaml.Node) (vOut *Value, errOut error) {
 			// Undo any effects on the environment. We *do* keep any named
 			// variables that were added to the vars map in case they were
 			// introduced within the element.
+			//
+			// TODO: If we change how we implement repeat nodes, we might be
+			// able to drop yamlEncoder.env and yamlDecoder.env.
 			dec.env = origEnv
 			// Add a generator function
 			gen = append(gen, func(e envSet) (*Value, envSet) {
@@ -444,7 +447,7 @@ func (c Closure) String() string {
 }
 
 func (v *Value) MarshalYAML() (any, error) {
-	enc := &yamlEncoder{}
+	enc := &yamlEncoder{e: topEnv}
 	return enc.value(v), nil
 }