diff --git a/.golangci.yml b/.golangci.yml
index 55573975..1bc38130 100644
--- a/.golangci.yml
+++ b/.golangci.yml
@@ -233,7 +233,7 @@ linters:
     - gochecknoinits # checks that no init functions are present in Go code
     - gochecksumtype # checks exhaustiveness on Go "sum types"
     #- gocognit # computes and checks the cognitive complexity of functions
-    #- goconst # finds repeated strings that could be replaced by a constant
+    - goconst # finds repeated strings that could be replaced by a constant
     #- gocritic # provides diagnostics that check for bugs, performance and style issues
     #- gocyclo # computes and checks the cyclomatic complexity of functions
     - godot # checks if comments end in a period
diff --git a/enforcer.go b/enforcer.go
index d5c3f557..52f11df4 100644
--- a/enforcer.go
+++ b/enforcer.go
@@ -22,6 +22,7 @@ import (
 	"sync"
 
 	"github.com/casbin/casbin/v2/effector"
+	casbinerrors "github.com/casbin/casbin/v2/errors"
 	"github.com/casbin/casbin/v2/log"
 	"github.com/casbin/casbin/v2/model"
 	"github.com/casbin/casbin/v2/persist"
@@ -29,7 +30,6 @@ import (
 	"github.com/casbin/casbin/v2/rbac"
 	defaultrolemanager "github.com/casbin/casbin/v2/rbac/default-role-manager"
 	"github.com/casbin/casbin/v2/util"
-
 	"github.com/casbin/govaluate"
 )
 
@@ -337,7 +337,7 @@ func (e *Enforcer) LoadPolicy() error {
 		}
 	}()
 
-	if err = e.adapter.LoadPolicy(newModel); err != nil && err.Error() != "invalid file path, file path cannot be empty" {
+	if err = e.adapter.LoadPolicy(newModel); err != nil && !errors.Is(err, casbinerrors.ErrInvalidFilePath) {
 		return err
 	}
 
@@ -410,7 +410,7 @@ func (e *Enforcer) loadFilteredPolicy(filter interface{}) error {
 	default:
 		return errors.New("filtered policies are not supported by this adapter")
 	}
-	if err := filteredAdapter.LoadFilteredPolicy(e.model, filter); err != nil && err.Error() != "invalid file path, file path cannot be empty" {
+	if err := filteredAdapter.LoadFilteredPolicy(e.model, filter); err != nil && !errors.Is(err, casbinerrors.ErrInvalidFilePath) {
 		return err
 	}
 
@@ -948,21 +948,23 @@ func (p enforceParameters) Get(name string) (interface{}, error) {
 		return nil, nil
 	}
 
+	err := errors.New("No parameter '" + name + "' found.")
+
 	switch name[0] {
 	case 'p':
 		i, ok := p.pTokens[name]
 		if !ok {
-			return nil, errors.New("No parameter '" + name + "' found.")
+			return nil, err
 		}
 		return p.pVals[i], nil
 	case 'r':
 		i, ok := p.rTokens[name]
 		if !ok {
-			return nil, errors.New("No parameter '" + name + "' found.")
+			return nil, err
 		}
 		return p.rVals[i], nil
 	default:
-		return nil, errors.New("No parameter '" + name + "' found.")
+		return nil, err
 	}
 }
 
diff --git a/enforcer_synced.go b/enforcer_synced.go
index 743f26c7..71adc195 100644
--- a/enforcer_synced.go
+++ b/enforcer_synced.go
@@ -15,10 +15,13 @@
 package casbin
 
 import (
+	"errors"
 	"sync"
 	"sync/atomic"
 	"time"
 
+	casbinerrors "github.com/casbin/casbin/v2/errors"
+
 	"github.com/casbin/govaluate"
 
 	"github.com/casbin/casbin/v2/persist"
@@ -132,7 +135,7 @@ func (e *SyncedEnforcer) LoadPolicyFast() error {
 	newRmMap := map[string]rbac.RoleManager{}
 	var err error
 
-	if err = e.adapter.LoadPolicy(newModel); err != nil && err.Error() != "invalid file path, file path cannot be empty" {
+	if err = e.adapter.LoadPolicy(newModel); err != nil && !errors.Is(err, casbinerrors.ErrInvalidFilePath) {
 		return err
 	}
 
diff --git a/errors/errors.go b/errors/errors.go
new file mode 100644
index 00000000..3c8b7a65
--- /dev/null
+++ b/errors/errors.go
@@ -0,0 +1,11 @@
+package errors
+
+import "errors"
+
+var (
+	ErrInvalidFilePath = errors.New("invalid file path, file path cannot be empty")
+)
+
+func Is(err, target error) bool {
+	return errors.Is(err, target)
+}
diff --git a/errors/rbac_errors.go b/errors/rbac_errors.go
index 247205ae..2f358b37 100644
--- a/errors/rbac_errors.go
+++ b/errors/rbac_errors.go
@@ -28,7 +28,3 @@ var (
 	ErrObjCondition   = errors.New("need to meet the prefix required by the object condition")
 	ErrEmptyCondition = errors.New("GetAllowedObjectConditions have an empty condition")
 )
-
-func Is(err, target error) bool {
-	return errors.Is(err, target)
-}
diff --git a/persist/file-adapter/adapter.go b/persist/file-adapter/adapter.go
index c68f0eaa..5ab86708 100644
--- a/persist/file-adapter/adapter.go
+++ b/persist/file-adapter/adapter.go
@@ -21,6 +21,7 @@ import (
 	"os"
 	"strings"
 
+	casbinerrors "github.com/casbin/casbin/v2/errors"
 	"github.com/casbin/casbin/v2/model"
 	"github.com/casbin/casbin/v2/persist"
 	"github.com/casbin/casbin/v2/util"
@@ -52,7 +53,7 @@ func NewAdapter(filePath string) *Adapter {
 // LoadPolicy loads all policy rules from the storage.
 func (a *Adapter) LoadPolicy(model model.Model) error {
 	if a.filePath == "" {
-		return errors.New("invalid file path, file path cannot be empty")
+		return casbinerrors.ErrInvalidFilePath
 	}
 
 	return a.loadPolicyFile(model, persist.LoadPolicyLine)
@@ -61,7 +62,7 @@ func (a *Adapter) LoadPolicy(model model.Model) error {
 // SavePolicy saves all policy rules to the storage.
 func (a *Adapter) SavePolicy(model model.Model) error {
 	if a.filePath == "" {
-		return errors.New("invalid file path, file path cannot be empty")
+		return casbinerrors.ErrInvalidFilePath
 	}
 
 	var tmp bytes.Buffer
diff --git a/persist/file-adapter/adapter_filtered.go b/persist/file-adapter/adapter_filtered.go
index 1a074c9a..62b41237 100644
--- a/persist/file-adapter/adapter_filtered.go
+++ b/persist/file-adapter/adapter_filtered.go
@@ -20,6 +20,7 @@ import (
 	"os"
 	"strings"
 
+	casbinerrors "github.com/casbin/casbin/v2/errors"
 	"github.com/casbin/casbin/v2/model"
 	"github.com/casbin/casbin/v2/persist"
 )
@@ -63,7 +64,7 @@ func (a *FilteredAdapter) LoadFilteredPolicy(model model.Model, filter interface
 		return a.LoadPolicy(model)
 	}
 	if a.filePath == "" {
-		return errors.New("invalid file path, file path cannot be empty")
+		return casbinerrors.ErrInvalidFilePath
 	}
 
 	filterValue, ok := filter.(*Filter)