diff --git a/solve/src/commonMain/kotlin/it/unibo/tuprolog/solve/Signature.kt b/solve/src/commonMain/kotlin/it/unibo/tuprolog/solve/Signature.kt
index 02c60ff46..ac068df91 100644
--- a/solve/src/commonMain/kotlin/it/unibo/tuprolog/solve/Signature.kt
+++ b/solve/src/commonMain/kotlin/it/unibo/tuprolog/solve/Signature.kt
@@ -93,9 +93,9 @@ data class Signature(
                             )
                         }
                         args.last().let {
-                            it is Struct && functor == varargStructFunctor && arity == 2 &&
-                                args.first().isInt &&
-                                args.last() == varargAtom
+                            it is Struct && it.functor == varargStructFunctor && it.arity == 2 &&
+                                it.args.first().isInt &&
+                                it.args.last() == varargAtom
                         } -> {
                             Signature(
                                 args.first().`as`<Atom>().value,
diff --git a/test-solve/src/commonTest/kotlin/it/unibo/tuprolog/solve/primitive/SignatureTest.kt b/test-solve/src/commonTest/kotlin/it/unibo/tuprolog/solve/primitive/SignatureTest.kt
index fe86b4856..1a180923a 100644
--- a/test-solve/src/commonTest/kotlin/it/unibo/tuprolog/solve/primitive/SignatureTest.kt
+++ b/test-solve/src/commonTest/kotlin/it/unibo/tuprolog/solve/primitive/SignatureTest.kt
@@ -100,7 +100,11 @@ internal class SignatureTest {
 
     @Test
     fun fromTermWithStructCreatesCorrectInstance() {
-        signatures.forEach { assertEquals(it, Signature.fromSignatureTerm(it.toTerm()) ?: fail()) }
+        signatures.forEach {
+            val reconstructed = Signature.fromSignatureTerm(it.toTerm())
+                ?: fail("Cannot reconstruct signature $it from it.toTerm(): ${it.toTerm()}")
+            assertEquals(it, reconstructed)
+        }
 
         signatureTerms.zip(signatures).forEach { (signatureTerm, signature) ->
             assertEquals(signature, Signature.fromSignatureTerm(signatureTerm) ?: fail())