diff --git a/internal/instance/resource_instance.go b/internal/instance/resource_instance.go
index de0b40f..1f9db3d 100644
--- a/internal/instance/resource_instance.go
+++ b/internal/instance/resource_instance.go
@@ -11,6 +11,7 @@ import (
 	"github.com/hashicorp/terraform-plugin-framework-validators/listvalidator"
 	"github.com/hashicorp/terraform-plugin-framework-validators/mapvalidator"
 	"github.com/hashicorp/terraform-plugin-framework-validators/stringvalidator"
+	"github.com/hashicorp/terraform-plugin-framework-validators/objectvalidator"
 	"github.com/hashicorp/terraform-plugin-framework/attr"
 	"github.com/hashicorp/terraform-plugin-framework/diag"
 	"github.com/hashicorp/terraform-plugin-framework/path"
@@ -116,6 +117,21 @@ func (r InstanceResource) Schema(_ context.Context, _ resource.SchemaRequest, re
 				PlanModifiers: []planmodifier.String{
 					stringplanmodifier.RequiresReplace(),
 				},
+        Validators: []validator.String{
+          stringvalidator.ConflictsWith(
+            path.Expressions{
+              path.MatchRoot("source_instance"), 
+              path.MatchRoot("source_file"),
+            }...
+          ),
+          stringvalidator.AtLeastOneOf(
+            path.Expressions{
+              path.MatchRoot("image"), 
+              path.MatchRoot("source_instance"), 
+              path.MatchRoot("source_file"),
+            }...
+          ),
+        },
 			},
 
 			"ephemeral": schema.BoolAttribute{
@@ -205,6 +221,20 @@ func (r InstanceResource) Schema(_ context.Context, _ resource.SchemaRequest, re
 				PlanModifiers: []planmodifier.Object{
 					objectplanmodifier.RequiresReplace(),
 				},
+        Validators: []validator.Object{
+          objectvalidator.ConflictsWith(
+            path.Expressions{
+              path.MatchRoot("image"), 
+              path.MatchRoot("source_file"),
+            }...),
+          objectvalidator.AtLeastOneOf(
+            path.Expressions{
+              path.MatchRoot("image"), 
+              path.MatchRoot("source_instance"), 
+              path.MatchRoot("source_file"),
+            }...
+          ),
+        },
 			},
 
 			"source_file": schema.StringAttribute{
@@ -212,9 +242,28 @@ func (r InstanceResource) Schema(_ context.Context, _ resource.SchemaRequest, re
 				PlanModifiers: []planmodifier.String{
 					stringplanmodifier.RequiresReplace(),
 				},
-				Validators: []validator.String{
+        Validators: []validator.String{
 					stringvalidator.LengthAtLeast(1),
-				},
+          stringvalidator.ConflictsWith(
+            path.Expressions{
+              path.MatchRoot("image"), 
+              path.MatchRoot("source_instance"),
+              path.MatchRoot("description"),
+              path.MatchRoot("type"),
+              path.MatchRoot("ephemeral"),
+              path.MatchRoot("profiles"),
+              path.MatchRoot("file"),
+              path.MatchRoot("config"),
+            }...
+          ),
+          stringvalidator.AtLeastOneOf(
+            path.Expressions{
+              path.MatchRoot("image"), 
+              path.MatchRoot("source_instance"), 
+              path.MatchRoot("source_file"),
+            }...
+          ),
+        },
 			},
 
 			// Computed.
@@ -383,29 +432,7 @@ func (r InstanceResource) ValidateConfig(ctx context.Context, req resource.Valid
 		)
 	}
 
-	if !atMostOneOf(config.Image, config.SourceFile, config.SourceInstance) {
-		resp.Diagnostics.AddError(
-			"Invalid Configuration",
-			"At most one of image, source_file and source_instance can be set.",
-		)
-		return
-	}
-
 	if !config.SourceFile.IsNull() {
-		// Instances from source_file are mutually exclusive with a series of other attributes.
-		if !config.Description.IsNull() ||
-			!config.Type.IsNull() ||
-			!config.Ephemeral.IsNull() ||
-			!config.Profiles.IsNull() ||
-			!config.Files.IsNull() ||
-			!config.Config.IsNull() {
-			resp.Diagnostics.AddError(
-				"Invalid Configuration",
-				"Attribute source_file is mutually exclusive with description, type, ephemeral, profiles, file and config.",
-			)
-			return
-		}
-
 		// With `incus import`, a storage pool can be provided optionally.
 		// In order to support the same behavior with source_file,
 		// a single device entry of type `disk` is allowed with exactly two properties