diff --git a/mapper/src/main/java/tw/com/softleader/data/jpa/spec/domain/SimpleSpecification.java b/mapper/src/main/java/tw/com/softleader/data/jpa/spec/domain/SimpleSpecification.java
index 37c9aba..64777bf 100644
--- a/mapper/src/main/java/tw/com/softleader/data/jpa/spec/domain/SimpleSpecification.java
+++ b/mapper/src/main/java/tw/com/softleader/data/jpa/spec/domain/SimpleSpecification.java
@@ -26,6 +26,7 @@
 
 import jakarta.persistence.criteria.Path;
 import jakarta.persistence.criteria.Root;
+import java.lang.reflect.InvocationTargetException;
 import java.util.Optional;
 import java.util.StringJoiner;
 import lombok.Builder;
@@ -63,8 +64,22 @@ private static <T> Specification<T> newSpec(
       @NonNull Class<? extends SimpleSpecification> domainClass,
       @NonNull String path,
       @NonNull Object value) {
-    return accessibleConstructor(domainClass, Context.class, String.class, Object.class)
-        .newInstance(context, path, value);
+    try {
+      return accessibleConstructor(domainClass, Context.class, String.class, Object.class)
+          .newInstance(context, path, value);
+    } catch (InvocationTargetException e) {
+      // Constructor.newInstance wraps any exception thrown inside the constructor in an
+      // InvocationTargetException; surface the original cause (e.g. TypeMismatchException,
+      // IllegalArgumentException) so it reaches SpecMapper.toSpec callers.
+      var cause = e.getCause();
+      if (cause instanceof RuntimeException runtimeException) {
+        throw runtimeException;
+      }
+      if (cause instanceof Error error) {
+        throw error;
+      }
+      throw new IllegalStateException(cause);
+    }
   }
 
   @SuppressWarnings({"unchecked"})
diff --git a/mapper/src/test/java/tw/com/softleader/data/jpa/spec/domain/BetweenTest.java b/mapper/src/test/java/tw/com/softleader/data/jpa/spec/domain/BetweenTest.java
index 15c89d6..60d6046 100644
--- a/mapper/src/test/java/tw/com/softleader/data/jpa/spec/domain/BetweenTest.java
+++ b/mapper/src/test/java/tw/com/softleader/data/jpa/spec/domain/BetweenTest.java
@@ -21,13 +21,19 @@
 package tw.com.softleader.data.jpa.spec.domain;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
 import static tw.com.softleader.data.jpa.spec.IntegrationTest.TestApplication.noopContext;
 
 import java.time.LocalDate;
 import java.util.Arrays;
+import java.util.List;
+import lombok.Builder;
+import lombok.Data;
 import org.junit.jupiter.api.Test;
 import org.springframework.beans.factory.annotation.Autowired;
 import tw.com.softleader.data.jpa.spec.IntegrationTest;
+import tw.com.softleader.data.jpa.spec.SpecMapper;
+import tw.com.softleader.data.jpa.spec.annotation.Spec;
 import tw.com.softleader.data.jpa.spec.usecase.Customer;
 import tw.com.softleader.data.jpa.spec.usecase.CustomerRepository;
 
@@ -49,4 +55,22 @@ void test() {
     var actual = repository.findAll(spec);
     assertThat(actual).hasSize(1).contains(matt);
   }
+
+  @Test
+  void oneElementThroughMapper() {
+    var mapper = SpecMapper.builder().build();
+    var birthday = List.of(LocalDate.now());
+    var criteria = BetweenCriteria.builder().birthday(birthday).build();
+    assertThatExceptionOfType(IllegalArgumentException.class)
+        .isThrownBy(() -> mapper.toSpec(criteria, Customer.class))
+        .withMessage("@Between expected exact 2 elements, but was " + birthday);
+  }
+
+  @Builder
+  @Data
+  static class BetweenCriteria {
+
+    @Spec(value = Between.class)
+    List<LocalDate> birthday;
+  }
 }
diff --git a/mapper/src/test/java/tw/com/softleader/data/jpa/spec/domain/InTest.java b/mapper/src/test/java/tw/com/softleader/data/jpa/spec/domain/InTest.java
index d01835e..b76149d 100644
--- a/mapper/src/test/java/tw/com/softleader/data/jpa/spec/domain/InTest.java
+++ b/mapper/src/test/java/tw/com/softleader/data/jpa/spec/domain/InTest.java
@@ -25,9 +25,13 @@
 import static tw.com.softleader.data.jpa.spec.IntegrationTest.TestApplication.noopContext;
 
 import java.util.Arrays;
+import lombok.Builder;
+import lombok.Data;
 import org.junit.jupiter.api.Test;
 import org.springframework.beans.factory.annotation.Autowired;
 import tw.com.softleader.data.jpa.spec.IntegrationTest;
+import tw.com.softleader.data.jpa.spec.SpecMapper;
+import tw.com.softleader.data.jpa.spec.annotation.Spec;
 import tw.com.softleader.data.jpa.spec.usecase.Customer;
 import tw.com.softleader.data.jpa.spec.usecase.CustomerRepository;
 
@@ -56,4 +60,22 @@ void typeMismatch() {
         .withMessage(
             "Failed to convert value of type 'java.lang.Object' to required type 'java.lang.Iterable'");
   }
+
+  @Test
+  void typeMismatchThroughMapper() {
+    var mapper = SpecMapper.builder().build();
+    var criteria = InCriteria.builder().name("matt").build();
+    assertThatExceptionOfType(TypeMismatchException.class)
+        .isThrownBy(() -> mapper.toSpec(criteria, Customer.class))
+        .withMessage(
+            "Failed to convert value of type 'java.lang.String' to required type 'java.lang.Iterable'");
+  }
+
+  @Builder
+  @Data
+  static class InCriteria {
+
+    @Spec(path = "name", value = In.class)
+    String name;
+  }
 }