diff --git a/backend/internal/pkg/antigravity/schema_const_test.go b/backend/internal/pkg/antigravity/schema_const_test.go
index ac83a4026c..05551fbd83 100644
--- a/backend/internal/pkg/antigravity/schema_const_test.go
+++ b/backend/internal/pkg/antigravity/schema_const_test.go
@@ -35,7 +35,8 @@ func TestBuildToolsPreservesStringConst(t *testing.T) {
 			}})
 			require.Len(t, tools, 1)
 			require.Len(t, tools[0].FunctionDeclarations, 1)
-			properties := tools[0].FunctionDeclarations[0].Parameters["properties"].(map[string]any)
+			properties, ok := tools[0].FunctionDeclarations[0].Parameters["properties"].(map[string]any)
+			require.True(t, ok, "tool parameters must contain a properties object")
 			got, err := json.Marshal(properties["action"])
 			require.NoError(t, err)
 			require.JSONEq(t, tc.want, string(got))