diff --git a/jsonschema/json_pointer.go b/jsonschema/json_pointer.go
index 90b4a2c..d7eb4a9 100644
--- a/jsonschema/json_pointer.go
+++ b/jsonschema/json_pointer.go
@@ -69,11 +69,7 @@ func parseJSONPointer(ptr string) (segments []string, err error) {
 // This implementation suffices for JSON Schema: pointers are applied only to Schemas,
 // and refer only to Schemas.
 func dereferenceJSONPointer(s *Schema, sptr string) (_ *Schema, err error) {
-	defer func() {
-		if err != nil {
-			err = fmt.Errorf("JSON Pointer %q: %w", sptr, err)
-		}
-	}()
+	defer wrapf(&err, "JSON Pointer %q", sptr)
 
 	segments, err := parseJSONPointer(sptr)
 	if err != nil {
diff --git a/jsonschema/util.go b/jsonschema/util.go
index 96b32dc..fcb632f 100644
--- a/jsonschema/util.go
+++ b/jsonschema/util.go
@@ -282,3 +282,10 @@ func assert(cond bool, msg string) {
 		panic("assertion failed: " + msg)
 	}
 }
+
+// wrapf wraps *errp with the given formatted message if *errp is not nil.
+func wrapf(errp *error, format string, args ...any) {
+	if *errp != nil {
+		*errp = fmt.Errorf("%s: %w", fmt.Sprintf(format, args...), *errp)
+	}
+}
diff --git a/jsonschema/validate.go b/jsonschema/validate.go
index 634417d..12a6242 100644
--- a/jsonschema/validate.go
+++ b/jsonschema/validate.go
@@ -42,11 +42,7 @@ type state struct {
 
 // validate validates the reflected value of the instance.
 func (st *state) validate(instance reflect.Value, schema *Schema, callerAnns *annotations) (err error) {
-	defer func() {
-		if err != nil {
-			err = fmt.Errorf("%s: %w", schema, err)
-		}
-	}()
+	defer wrapf(&err, "validating %s", schema)
 
 	st.stack = append(st.stack, schema) // push
 	defer func() {