diff --git a/preset.go b/preset.go
index 0e5ca74..c9ee1ae 100644
--- a/preset.go
+++ b/preset.go
@@ -2,7 +2,6 @@ package preview
 
 import (
 	"fmt"
-	"slices"
 
 	"github.com/aquasecurity/trivy/pkg/iac/terraform"
 	"github.com/hashicorp/hcl/v2"
@@ -32,24 +31,6 @@ func presets(modules terraform.Modules, parameters []types.Parameter) []types.Pr
 				defaultPreset = &preset
 			}
 
-			for paramName, paramValue := range preset.Parameters {
-				templateParamIndex := slices.IndexFunc(parameters, func(p types.Parameter) bool {
-					return p.Name == paramName
-				})
-				if templateParamIndex == -1 {
-					preset.Diagnostics = append(preset.Diagnostics, &hcl.Diagnostic{
-						Severity: hcl.DiagError,
-						Summary:  "Undefined Parameter",
-						Detail:   fmt.Sprintf("Preset parameter %q is not defined by the template.", paramName),
-					})
-					continue
-				}
-				templateParam := parameters[templateParamIndex]
-				for _, diag := range templateParam.Valid(types.StringLiteral(paramValue)) {
-					preset.Diagnostics = append(preset.Diagnostics, diag)
-				}
-			}
-
 			foundPresets = append(foundPresets, preset)
 		}
 	}
diff --git a/preview.go b/preview.go
index aae478c..f157509 100644
--- a/preview.go
+++ b/preview.go
@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io/fs"
 	"log/slog"
+	"slices"
 
 	"github.com/aquasecurity/trivy/pkg/iac/scanners/terraform/parser"
 	"github.com/hashicorp/hcl/v2"
@@ -106,6 +107,21 @@ func ValidatePrebuilds(ctx context.Context, input Input, preValid []types.Preset
 			continue
 		}
 
+		// Check all parameters in the preset are defined by the template.
+		for paramName, _ := range pre.Parameters {
+			templateParamIndex := slices.IndexFunc(output.Parameters, func(p types.Parameter) bool {
+				return p.Name == paramName
+			})
+			if templateParamIndex == -1 {
+				pre.Diagnostics = append(pre.Diagnostics, &hcl.Diagnostic{
+					Severity: hcl.DiagError,
+					Summary:  "Undefined Parameter",
+					Detail:   fmt.Sprintf("Preset parameter %q is not defined by the template.", paramName),
+				})
+				continue
+			}
+		}
+
 		// If any parameter is invalid, then the preset is invalid.
 		// A value must be specified for this failing parameter.
 		for _, param := range output.Parameters {
diff --git a/preview_test.go b/preview_test.go
index 0c2e0da..5bd4821 100644
--- a/preview_test.go
+++ b/preview_test.go
@@ -714,6 +714,17 @@ func TestPresetValidation(t *testing.T) {
 				"not_prebuild":           aPre().noDiagnostics().prebuildCount(0),
 			},
 		},
+		{
+			name:  "preset ok",
+			dir:   "presetok",
+			input: preview.Input{},
+			presetAssert: map[string]assertPreset{
+				"valid_preset": aPre().
+					value("use_custom_image", "true").
+					value("custom_image_url", "docker.io/codercom/test:latest").
+					noDiagnostics(),
+			},
+		},
 	} {
 		t.Run(tc.name, func(t *testing.T) {
 			t.Parallel()
diff --git a/testdata/invalidpresets/main.tf b/testdata/invalidpresets/main.tf
index a7afc28..854d68c 100644
--- a/testdata/invalidpresets/main.tf
+++ b/testdata/invalidpresets/main.tf
@@ -18,11 +18,17 @@ data "coder_parameter" "valid_parameter" {
 
 data "coder_workspace_preset" "no_parameters" {
   name = "no_parameters"
+  prebuilds {
+    instances = 1
+  }
 }
 
 data "coder_workspace_preset" "empty_parameters" {
   name = "empty_parameters"
   parameters = {}
+  prebuilds {
+    instances = 1
+  }
 }
 
 data "coder_workspace_preset" "invalid_parameter_name" {
@@ -30,6 +36,9 @@ data "coder_workspace_preset" "invalid_parameter_name" {
   parameters = {
     "invalid_parameter_name" = "irrelevant_value"
   }
+  prebuilds {
+    instances = 1
+  }
 }
 
 data "coder_workspace_preset" "invalid_parameter_value" {
@@ -37,6 +46,9 @@ data "coder_workspace_preset" "invalid_parameter_value" {
   parameters = {
     "valid_parameter_name" = "invalid_value"
   }
+  prebuilds {
+    instances = 1
+  }
 }
 
 data "coder_workspace_preset" "valid_preset" {
@@ -44,6 +56,10 @@ data "coder_workspace_preset" "valid_preset" {
   parameters = {
     "valid_parameter_name" = "valid_option_value"
   }
+  prebuilds {
+    instances = 1
+  }
+
 }
 
 data "coder_workspace_preset" "another_default_preset" {
@@ -52,6 +68,9 @@ data "coder_workspace_preset" "another_default_preset" {
     "valid_parameter_name" = "valid_option_value"
   }
   default = true
+  prebuilds {
+    instances = 1
+  }
 }
 
 data "coder_workspace_preset" "default_preset" {
@@ -60,5 +79,8 @@ data "coder_workspace_preset" "default_preset" {
     "valid_parameter_name" = "valid_option_value"
   }
   default = true
+  prebuilds {
+    instances = 1
+  }
 }
 
diff --git a/testdata/presetok/main.tf b/testdata/presetok/main.tf
new file mode 100644
index 0000000..2ada518
--- /dev/null
+++ b/testdata/presetok/main.tf
@@ -0,0 +1,32 @@
+terraform {
+  required_providers {
+    coder = {
+      source = "coder/coder"
+      version = "2.8.0"
+    }
+  }
+}
+
+data "coder_parameter" "use_custom_image" {
+  name    = "use_custom_image"
+  type    = "bool"
+  default = "false"
+}
+
+data "coder_parameter" "custom_image_url" {
+  count   = data.coder_parameter.use_custom_image.value == "true" ? 1 : 0
+  name    = "custom_image_url"
+  type    = "string"
+  # No default - required when shown
+}
+
+data "coder_workspace_preset" "valid_preset" {
+  name = "valid_preset"
+  parameters = {
+    "use_custom_image" = "true"
+    "custom_image_url" = "docker.io/codercom/test:latest"
+  }
+  prebuilds {
+    instances = 1
+  }
+}
\ No newline at end of file