diff --git a/docs/changelog.md b/docs/changelog.md
index 912518d4..e38b81d3 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -15,11 +15,12 @@ pages](https://github.com/dalibo/ldap2pg/pulls?utf8=%E2%9C%93&q=is%3Apr%20is%3Am
 
 - Fix memory usage value.
 - Experimental GSSAPI authentication method.
-- Run CI on rockylinux 10 with PostgreSQL19 beta1
-- Bump PostgreSQL developpement version to 18
+- Run CI on rockylinux 10 with PostgreSQL19 beta1.
+- Bump PostgreSQL developpement version to 18.
 - Fix duplicate CREATE ROLE.
 - Resolve ~ in path.
 - Fix empty filter in configuration file leading to panic.
+- Strict yaml configuration file decoding.
 
 
 # ldap2pg 6.5.1
diff --git a/internal/cmd/ldap2pg.go b/internal/cmd/ldap2pg.go
index e6b3ed4d..d91e4a1a 100644
--- a/internal/cmd/ldap2pg.go
+++ b/internal/cmd/ldap2pg.go
@@ -40,11 +40,8 @@ func Main() {
 	}
 
 	if err != nil {
-		if errs, ok := err.(interface{ Len() int }); ok {
-			// Assume error are already logged before.
-			slog.Error("Some errors occurred. See above for more details.", "err", err, "count", errs.Len())
-		} else {
-			slog.Error("Fatal error.", "err", err)
+		for _, werr := range errorlist.Unwrap(err) {
+			slog.Error(werr.Error())
 		}
 		if internal.CurrentLevel > slog.LevelDebug {
 			slog.Error("Run ldap2pg with --verbose to get more informations.")
diff --git a/internal/config/yaml.go b/internal/config/yaml.go
index d6bd12b7..b12843fc 100644
--- a/internal/config/yaml.go
+++ b/internal/config/yaml.go
@@ -8,7 +8,9 @@ import (
 	"log/slog"
 	"os"
 	"reflect"
+	"strings"
 
+	"github.com/dalibo/ldap2pg/v6/internal/errorlist"
 	"github.com/dalibo/ldap2pg/v6/internal/ldap"
 	"github.com/dalibo/ldap2pg/v6/internal/postgres"
 	"github.com/dalibo/ldap2pg/v6/internal/pyfmt"
@@ -83,11 +85,24 @@ func (c *Config) DecodeYaml(yaml any) (err error) {
 		Metadata:         &mapstructure.Metadata{},
 		Result:           c,
 		WeaklyTypedInput: true,
+		ErrorUnused:      true,
 	})
 	if err != nil {
 		return
 	}
 	err = d.Decode(yaml)
+
+	// Converting joined error into errorlist.
+	// Lower the error message to align it with the LDAP parameters.
+	yamlErrors := errorlist.New("invalid configuration file")
+	for _, werr := range errorlist.Unwrap(err) {
+		lowerErr := strings.ToLower(werr.Error())
+		if !yamlErrors.Append(fmt.Errorf("%s", lowerErr)) {
+			err = yamlErrors.Value()
+			return
+		}
+	}
+	err = yamlErrors.Value()
 	return
 }
 
diff --git a/internal/config/yaml_test.go b/internal/config/yaml_test.go
index 97a15acc..fa79ca36 100644
--- a/internal/config/yaml_test.go
+++ b/internal/config/yaml_test.go
@@ -4,6 +4,7 @@ import (
 	"testing"
 
 	"github.com/dalibo/ldap2pg/v6/internal/config"
+	"github.com/dalibo/ldap2pg/v6/internal/errorlist"
 	"github.com/lithammer/dedent"
 	"github.com/stretchr/testify/require"
 	"gopkg.in/yaml.v3"
@@ -31,3 +32,26 @@ func TestLoadPrivilege(t *testing.T) {
 	r.Equal("CONNECT", p[0].Type)
 	r.Equal("DATABASE", p[0].On)
 }
+
+func TestStrictYaml(t *testing.T) {
+	r := require.New(t)
+
+	rawYaml := dedent.Dedent(`
+	postgres:
+	  uri: "postgres://user:xx@localhost"
+	  roles_blacklist_query: [postgres]
+	  databases_query: [nominal]
+	ldap:
+	  password: "secret"
+	`)
+	var value map[string]any
+	yaml.Unmarshal([]byte(rawYaml), &value) //nolint:errcheck
+
+	c := config.New()
+	err := c.DecodeYaml(value)
+	r.EqualError(err, "invalid configuration file\n'ldap' has invalid keys: password\n'postgres' has invalid keys: uri")
+	errs := errorlist.Unwrap(err)
+	r.Len(errs, 3)
+	r.EqualError(errs[1], "'ldap' has invalid keys: password")
+	r.EqualError(errs[2], "'postgres' has invalid keys: uri")
+}
diff --git a/internal/errorlist/errorlist.go b/internal/errorlist/errorlist.go
index 26b56280..70e53731 100644
--- a/internal/errorlist/errorlist.go
+++ b/internal/errorlist/errorlist.go
@@ -77,8 +77,8 @@ func (errl *List) Value() error {
 	case 0:
 		return nil
 	case 1:
-		return errl.errors[0]
+		return fmt.Errorf("%s: %w", errl.message, errl.errors[0])
 	default:
-		return errl
+		return errors.Join(append([]error{errors.New(errl.message)}, errl.errors...)...)
 	}
 }
diff --git a/internal/errorlist/errorlist_test.go b/internal/errorlist/errorlist_test.go
index a45cbe6e..cf913005 100644
--- a/internal/errorlist/errorlist_test.go
+++ b/internal/errorlist/errorlist_test.go
@@ -35,3 +35,20 @@ func buildErrors(n int) []error {
 	}
 	return errors
 }
+
+func TestErrorListValue(t *testing.T) {
+	r := require.New(t)
+
+	err := errorlist.New("context")
+	err.Append(fmt.Errorf("content"))
+	errs := errorlist.Unwrap(err.Value())
+	r.Equal(1, len(errs))
+	r.Equal("context: content", errs[0].Error())
+
+	err.Append(fmt.Errorf("content 2"))
+	errs = errorlist.Unwrap(err.Value())
+	r.Equal(3, len(errs))
+	r.Equal("context", errs[0].Error())
+	r.Equal("content", errs[1].Error())
+	r.Equal("content 2", errs[2].Error())
+}