diff --git a/proxmoxtf/utils.go b/proxmoxtf/utils.go
index dfba77d1..bf8f9298 100644
--- a/proxmoxtf/utils.go
+++ b/proxmoxtf/utils.go
@@ -98,7 +98,7 @@ func getCPUFlagsValidator() schema.SchemaValidateDiagFunc {
 }
 
 func getCPUTypeValidator() schema.SchemaValidateDiagFunc {
-	return validation.ToDiagFunc(validation.StringInSlice([]string{
+	standardTypes := []string{
 		"486",
 		"Broadwell",
 		"Broadwell-IBRS",
@@ -144,7 +144,12 @@ func getCPUTypeValidator() schema.SchemaValidateDiagFunc {
 		"phenom",
 		"qemu32",
 		"qemu64",
-	}, false))
+	}
+
+	return validation.ToDiagFunc(validation.Any(
+		validation.StringInSlice(standardTypes, false),
+		validation.StringMatch(regexp.MustCompile(`^custom-.+$`), "must be a valid custom CPU type"),
+	))
 }
 
 func getFileFormatValidator() schema.SchemaValidateDiagFunc {
diff --git a/proxmoxtf/utils_test.go b/proxmoxtf/utils_test.go
new file mode 100644
index 00000000..48b25d98
--- /dev/null
+++ b/proxmoxtf/utils_test.go
@@ -0,0 +1,37 @@
+/*
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/.
+ */
+
+package proxmoxtf
+
+import (
+	"testing"
+)
+
+func Test_getCPUTypeValidator(t *testing.T) {
+	t.Parallel()
+	tests := []struct {
+		name  string
+		value string
+		valid bool
+	}{
+		{"empty", "", false},
+		{"invalid", "invalid", false},
+		{"valid", "host", true},
+		{"valid", "qemu64", true},
+		{"valid", "custom-abc", true},
+	}
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			f := getCPUTypeValidator()
+			res := f(tt.value, nil)
+			if !res.HasError() != tt.valid {
+				t.Errorf("validate: '%s', want %v got %v", tt.value, tt.valid, res)
+			}
+		})
+	}
+}