diff --git a/sadu-queries/src/main/java/de/chojo/sadu/queries/exception/Check.java b/sadu-queries/src/main/java/de/chojo/sadu/queries/exception/Check.java
new file mode 100644
index 00000000..16929bc5
--- /dev/null
+++ b/sadu-queries/src/main/java/de/chojo/sadu/queries/exception/Check.java
@@ -0,0 +1,23 @@
+/*
+ *     SPDX-License-Identifier: LGPL-3.0-or-later
+ *
+ *     Copyright (C) RainbowDashLabs and Contributor
+ */
+
+package de.chojo.sadu.queries.exception;
+
+import de.chojo.sadu.mapper.wrapper.Row;
+import org.jetbrains.annotations.Nullable;
+
+import java.sql.ResultSet;
+
+public final class Check {
+    public static void assertQueryResult(@Nullable Object object) {
+        if (object instanceof Row) {
+            throw new IllegalQueryReturnTypeException("Result is of type Row. Using a row mapper to map to a Row is forbidden. Rows are mutable and are no longer accessible after query execution.");
+        }
+        if (object instanceof ResultSet) {
+            throw new IllegalQueryReturnTypeException("Result is of type ResultSet. Using a row mapper to map to a ResultSet is forbidden. ResultSets are mutable and are no longer accessible after query execution.");
+        }
+    }
+}
diff --git a/sadu-queries/src/main/java/de/chojo/sadu/queries/exception/IllegalQueryReturnTypeException.java b/sadu-queries/src/main/java/de/chojo/sadu/queries/exception/IllegalQueryReturnTypeException.java
new file mode 100644
index 00000000..ee8ac921
--- /dev/null
+++ b/sadu-queries/src/main/java/de/chojo/sadu/queries/exception/IllegalQueryReturnTypeException.java
@@ -0,0 +1,13 @@
+/*
+ *     SPDX-License-Identifier: LGPL-3.0-or-later
+ *
+ *     Copyright (C) RainbowDashLabs and Contributor
+ */
+
+package de.chojo.sadu.queries.exception;
+
+public class IllegalQueryReturnTypeException extends RuntimeException{
+    public IllegalQueryReturnTypeException(String message) {
+        super(message);
+    }
+}
diff --git a/sadu-queries/src/main/java/de/chojo/sadu/queries/execution/reading/ReaderImpl.java b/sadu-queries/src/main/java/de/chojo/sadu/queries/execution/reading/ReaderImpl.java
index 938b7350..19d977f8 100644
--- a/sadu-queries/src/main/java/de/chojo/sadu/queries/execution/reading/ReaderImpl.java
+++ b/sadu-queries/src/main/java/de/chojo/sadu/queries/execution/reading/ReaderImpl.java
@@ -15,6 +15,7 @@
 import de.chojo.sadu.queries.api.query.AppendedQuery;
 import de.chojo.sadu.queries.api.results.reading.Result;
 import de.chojo.sadu.queries.call.CallImpl;
+import de.chojo.sadu.queries.exception.Check;
 import de.chojo.sadu.queries.query.AppendedQueryImpl;
 import de.chojo.sadu.queries.query.QueryImpl;
 import de.chojo.sadu.queries.query.TokenizedQuery;
@@ -70,7 +71,9 @@ private SingleResult<V> mapOne() {
                 ((CallImpl) call()).apply(sql(), stmt);
                 var resultSet = stmt.executeQuery();
                 if (resultSet.next()) {
-                    return new SingleResult<>(this, mapper(resultSet).map(new Row(resultSet, mapperConfig())));
+                    V mapped = mapper(resultSet).map(new Row(resultSet, mapperConfig()));
+                    Check.assertQueryResult(mapped);
+                    return new SingleResult<>(this, mapped);
                 }
             }
             return new SingleResult<>(this, null);
@@ -85,7 +88,11 @@ private MultiResult<List<V>> mapAll() {
                 ((CallImpl) call()).apply(sql(), stmt);
                 var resultSet = stmt.executeQuery();
                 var row = new Row(resultSet, mapperConfig());
-                while (resultSet.next()) result.add(mapper(resultSet).map(row));
+                while (resultSet.next()) {
+                    V mapped = mapper(resultSet).map(row);
+                    Check.assertQueryResult(mapped);
+                    result.add(mapped);
+                }
             }
             return new MultiResult<>(this, result);
         });