diff --git a/lib/challenge/register.go b/lib/challenge/register.go
index 449b975..a92c336 100644
--- a/lib/challenge/register.go
+++ b/lib/challenge/register.go
@@ -11,6 +11,7 @@ import (
 	"github.com/go-jose/go-jose/v4/jwt"
 	"github.com/goccy/go-yaml/ast"
 	"github.com/google/cel-go/cel"
+	"github.com/google/cel-go/common/types"
 	"io"
 	"math/rand/v2"
 	"net/http"
@@ -71,6 +72,13 @@ func (r Register) Create(state StateInterface, name string, pol policy.Challenge
 		if err != nil {
 			return nil, 0, fmt.Errorf("error compiling conditions: %v", err)
 		}
+
+		if out := ast.OutputType(); out == nil {
+			return nil, 0, fmt.Errorf("error compiling conditions: no output")
+		} else if out != types.BoolType {
+			return nil, 0, fmt.Errorf("error compiling conditions: output type is not bool")
+		}
+
 		reg.Condition, err = http_cel.ProgramAst(state.ProgramEnv(), ast)
 		if err != nil {
 			return nil, 0, fmt.Errorf("error compiling program: %v", err)
diff --git a/lib/rule.go b/lib/rule.go
index 2fd5670..c43f41b 100644
--- a/lib/rule.go
+++ b/lib/rule.go
@@ -71,6 +71,12 @@ func NewRuleState(state challenge.StateInterface, r policy.Rule, replacer *strin
 			return RuleState{}, fmt.Errorf("error compiling conditions: %w", err)
 		}
 
+		if out := ast.OutputType(); out == nil {
+			return RuleState{}, fmt.Errorf("error compiling conditions: no output")
+		} else if out != types.BoolType {
+			return RuleState{}, fmt.Errorf("error compiling conditions: output type is not bool")
+		}
+
 		program, err := http_cel.ProgramAst(state.ProgramEnv(), ast)
 		if err != nil {
 			return RuleState{}, fmt.Errorf("error compiling program: %w", err)
diff --git a/lib/state.go b/lib/state.go
index d820d71..1524262 100644
--- a/lib/state.go
+++ b/lib/state.go
@@ -13,6 +13,7 @@ import (
 	"git.gammaspectra.live/git/go-away/lib/settings"
 	"git.gammaspectra.live/git/go-away/utils"
 	"github.com/google/cel-go/cel"
+	"github.com/google/cel-go/common/types"
 	"github.com/yl2chen/cidranger"
 	"golang.org/x/net/html"
 	"log/slog"
@@ -210,6 +211,12 @@ func NewState(p policy.Policy, opt settings.Settings, settings policy.StateSetti
 			return nil, fmt.Errorf("conditions %s: error compiling conditions: %v", k, err)
 		}
 
+		if out := ast.OutputType(); out == nil {
+			return nil, fmt.Errorf("conditions %s: error compiling conditions: no output", k)
+		} else if out != types.BoolType {
+			return nil, fmt.Errorf("conditions %s: error compiling conditions: output type is not bool", k)
+		}
+
 		cond, err := cel.AstToString(ast)
 		if err != nil {
 			return nil, fmt.Errorf("conditions %s: error printing condition: %v", k, err)