diff --git a/session/create.go b/session/create.go
index a2d2b99..35d0540 100644
--- a/session/create.go
+++ b/session/create.go
@@ -4,7 +4,6 @@ import (
 	"context"
 	"crypto/ecdsa"
 
-	"github.com/nspcc-dev/neofs-api-go/internal"
 	"github.com/nspcc-dev/neofs-api-go/service"
 	crypto "github.com/nspcc-dev/neofs-crypto"
 	"google.golang.org/grpc"
@@ -18,10 +17,6 @@ type gRPCCreator struct {
 	clientFunc func(*grpc.ClientConn) SessionClient
 }
 
-const ErrNilCreateParamsSource = internal.Error("create params source is nil")
-
-const ErrNilGPRCClientConn = internal.Error("gRPC client connection is nil")
-
 // NewGRPCCreator unites virtual gRPC client with private ket and returns Creator interface.
 //
 // If passed ClientConn is nil, ErrNilGPRCClientConn returns.
diff --git a/session/errors.go b/session/errors.go
new file mode 100644
index 0000000..3a9c129
--- /dev/null
+++ b/session/errors.go
@@ -0,0 +1,15 @@
+package session
+
+import "github.com/nspcc-dev/neofs-api-go/internal"
+
+// ErrNilCreateParamsSource is returned by functions that expect a non-nil
+// CreateParamsSource, but received nil.
+const ErrNilCreateParamsSource = internal.Error("create params source is nil")
+
+// ErrNilGPRCClientConn is returned by functions that expect a non-nil
+// grpc.ClientConn, but received nil.
+const ErrNilGPRCClientConn = internal.Error("gRPC client connection is nil")
+
+// ErrPrivateTokenNotFound is returned when addressed private token was
+// not found in storage.
+const ErrPrivateTokenNotFound = internal.Error("private token not found")
diff --git a/session/types.go b/session/types.go
index 9e8db48..932fe38 100644
--- a/session/types.go
+++ b/session/types.go
@@ -4,7 +4,6 @@ import (
 	"context"
 	"crypto/ecdsa"
 
-	"github.com/nspcc-dev/neofs-api-go/internal"
 	"github.com/nspcc-dev/neofs-api-go/refs"
 	"github.com/nspcc-dev/neofs-api-go/service"
 )
@@ -79,6 +78,3 @@ type CreateResult interface {
 type Creator interface {
 	Create(context.Context, CreateParamsSource) (CreateResult, error)
 }
-
-// ErrPrivateTokenNotFound is raised when addressed private token was not found in storage.
-const ErrPrivateTokenNotFound = internal.Error("private token not found")