diff --git a/sql/src/main/java/org/apache/druid/sql/calcite/planner/CalciteRulesManager.java b/sql/src/main/java/org/apache/druid/sql/calcite/planner/CalciteRulesManager.java
index 829c44b18c60..8d3b6a743e38 100644
--- a/sql/src/main/java/org/apache/druid/sql/calcite/planner/CalciteRulesManager.java
+++ b/sql/src/main/java/org/apache/druid/sql/calcite/planner/CalciteRulesManager.java
@@ -61,6 +61,7 @@
 import org.apache.druid.sql.calcite.rule.FilterDecomposeCoalesceRule;
 import org.apache.druid.sql.calcite.rule.FilterDecomposeConcatRule;
 import org.apache.druid.sql.calcite.rule.FilterJoinExcludePushToChildRule;
+import org.apache.druid.sql.calcite.rule.FixIncorrectInExpansionTypes;
 import org.apache.druid.sql.calcite.rule.FlattenConcatRule;
 import org.apache.druid.sql.calcite.rule.ProjectAggregatePruneUnusedCallRule;
 import org.apache.druid.sql.calcite.rule.ReverseLookupRule;
@@ -71,6 +72,7 @@
 import org.apache.druid.sql.calcite.run.EngineFeature;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.Set;
 
@@ -291,6 +293,7 @@ private Program buildPreProgram(final PlannerContext plannerContext, final boole
     // Program that pre-processes the tree before letting the full-on VolcanoPlanner loose.
     final List<Program> prePrograms = new ArrayList<>();
     prePrograms.add(new LoggingProgram("Start", isDebug));
+    prePrograms.add(sqlToRelWorkaroundProgram());
     prePrograms.add(Programs.subQuery(DefaultRelMetadataProvider.INSTANCE));
     prePrograms.add(new LoggingProgram("Finished subquery program", isDebug));
     prePrograms.add(DecorrelateAndTrimFieldsProgram.INSTANCE);
@@ -306,6 +309,12 @@ private Program buildPreProgram(final PlannerContext plannerContext, final boole
     return Programs.sequence(prePrograms.toArray(new Program[0]));
   }
 
+  private Program sqlToRelWorkaroundProgram()
+  {
+    Set<RelOptRule> rules = Collections.singleton(new FixIncorrectInExpansionTypes());
+    return Programs.hep(rules, true, DefaultRelMetadataProvider.INSTANCE);
+  }
+
   /**
    * Program to perform manipulations on the logical tree prior to starting the cost-based planner. Mainly this
    * helps the cost-based planner finish faster, and helps the decoupled planner generate the same plans as the
diff --git a/sql/src/main/java/org/apache/druid/sql/calcite/rule/FixIncorrectInExpansionTypes.java b/sql/src/main/java/org/apache/druid/sql/calcite/rule/FixIncorrectInExpansionTypes.java
new file mode 100644
index 000000000000..9c049ac89dab
--- /dev/null
+++ b/sql/src/main/java/org/apache/druid/sql/calcite/rule/FixIncorrectInExpansionTypes.java
@@ -0,0 +1,97 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.apache.druid.sql.calcite.rule;
+
+import org.apache.calcite.plan.RelOptRule;
+import org.apache.calcite.plan.RelOptRuleCall;
+import org.apache.calcite.rel.RelNode;
+import org.apache.calcite.rel.rules.SubstitutionRule;
+import org.apache.calcite.rex.RexBuilder;
+import org.apache.calcite.rex.RexCall;
+import org.apache.calcite.rex.RexNode;
+import org.apache.calcite.rex.RexShuttle;
+import org.apache.calcite.rex.RexUtil;
+import org.apache.calcite.sql.SqlKind;
+import org.apache.calcite.sql.type.SqlTypeName;
+
+/**
+ * Rewrites comparisions to avoid bug FIXME.
+ *
+ * Rewrites RexCall::VARCHAR = RexLiteral::CHAR to RexCall::VARCHAR =
+ * RexLiteral::VARCHAR
+ *
+ * needed until CALCITE-6435 is fixed & released.
+ */
+public class FixIncorrectInExpansionTypes extends RelOptRule implements SubstitutionRule
+{
+  public FixIncorrectInExpansionTypes()
+  {
+    super(operand(RelNode.class, any()));
+  }
+
+  @Override
+  public void onMatch(RelOptRuleCall call)
+  {
+    final RelNode oldNode = call.rel(0);
+    final RewriteShuttle shuttle = new RewriteShuttle(oldNode.getCluster().getRexBuilder());
+    final RelNode newNode = oldNode.accept(shuttle);
+
+    // noinspection ObjectEquality
+    if (newNode != oldNode) {
+      call.transformTo(newNode);
+      call.getPlanner().prune(oldNode);
+    }
+  }
+
+  private static class RewriteShuttle extends RexShuttle
+  {
+    private final RexBuilder rexBuilder;
+
+    public RewriteShuttle(RexBuilder rexBuilder)
+    {
+      this.rexBuilder = rexBuilder;
+    }
+
+    @Override
+    public RexNode visitCall(RexCall call)
+    {
+      RexNode newNode = super.visitCall(call);
+      if (newNode.getKind() == SqlKind.EQUALS || newNode.getKind() == SqlKind.NOT_EQUALS) {
+        RexCall newCall = (RexCall) newNode;
+        RexNode op0 = newCall.getOperands().get(0);
+        RexNode op1 = newCall.getOperands().get(1);
+        if (RexUtil.isLiteral(op1, false)) {
+
+          if (op1.getType().getSqlTypeName() == SqlTypeName.CHAR
+              && op0.getType().getSqlTypeName() == SqlTypeName.VARCHAR) {
+
+            RexNode newLiteral = rexBuilder.ensureType(op0.getType(), op1, true);
+            return rexBuilder.makeCall(
+                newCall.getOperator(),
+                op0,
+                newLiteral
+            );
+          }
+        }
+      }
+      return newNode;
+    }
+  }
+}
diff --git a/sql/src/test/java/org/apache/druid/sql/calcite/CalciteSelectQueryTest.java b/sql/src/test/java/org/apache/druid/sql/calcite/CalciteSelectQueryTest.java
index d1f256207d54..d2699e77f79b 100644
--- a/sql/src/test/java/org/apache/druid/sql/calcite/CalciteSelectQueryTest.java
+++ b/sql/src/test/java/org/apache/druid/sql/calcite/CalciteSelectQueryTest.java
@@ -21,6 +21,7 @@
 
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
+import org.apache.calcite.rel.RelNode;
 import org.apache.druid.common.config.NullHandling;
 import org.apache.druid.error.DruidExceptionMatcher;
 import org.apache.druid.java.util.common.DateTimes;
@@ -61,6 +62,8 @@
 import java.util.List;
 import java.util.Map;
 
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
 public class CalciteSelectQueryTest extends BaseCalciteQueryTest
 {
   @Test
@@ -2175,4 +2178,28 @@ public void testCacheKeyConsistency()
         )
         .run();
   }
+
+  @Test
+  public void testSqlToRelInConversion()
+  {
+    assertEquals(
+        "1.37.0",
+        RelNode.class.getPackage().getImplementationVersion(),
+        "Calcite version changed; check if CALCITE-6435 is fixed and remove:\n * method CalciteRulesManager#sqlToRelWorkaroundProgram\n * FixIncorrectInExpansionTypes class\n* this assertion"
+    );
+
+    testBuilder()
+        .sql(
+            "SELECT channel FROM wikipedia\n"
+                + "WHERE channel in ('#en.wikipedia') and channel = '#en.wikipedia' and\n"
+                + "isRobot = 'false'\n"
+                + "LIMIT 1"
+        )
+        .expectedResults(
+            ImmutableList.of(
+                new Object[] {"#en.wikipedia"}
+            )
+        )
+        .run();
+  }
 }
diff --git a/sql/src/test/quidem/org.apache.druid.quidem.SqlQuidemTest/decoupled.iq b/sql/src/test/quidem/org.apache.druid.quidem.SqlQuidemTest/decoupled.iq
index be52c7c4c65b..530bbe172bb9 100644
--- a/sql/src/test/quidem/org.apache.druid.quidem.SqlQuidemTest/decoupled.iq
+++ b/sql/src/test/quidem/org.apache.druid.quidem.SqlQuidemTest/decoupled.iq
@@ -26,13 +26,13 @@ LogicalSort(sort0=[$0], dir0=[ASC])
 LogicalSort(sort0=[$0], dir0=[ASC])
   LogicalAggregate(group=[{0}], cnt=[COUNT($1) FILTER $2], aall=[COUNT()])
     LogicalProject(cityName=[$2], channel=[$1], $f3=[IS TRUE(>($17, 0))])
-      LogicalFilter(condition=[SEARCH($2, Sarg['Aarhus':VARCHAR(8), 'New York':VARCHAR(8)]:VARCHAR(8))])
+      LogicalFilter(condition=[SEARCH($2, Sarg['Aarhus':VARCHAR, 'New York':VARCHAR]:VARCHAR)])
         LogicalTableScan(table=[[druid, wikipedia]])
 
 !logicalPlan
 DruidAggregate(group=[{0}], cnt=[COUNT($1) FILTER $2], aall=[COUNT()], druid=[logical])
   DruidProject(cityName=[$2], channel=[$1], $f3=[IS TRUE(>($17, 0))], druid=[logical])
-    DruidFilter(condition=[SEARCH($2, Sarg['Aarhus':VARCHAR(8), 'New York':VARCHAR(8)]:VARCHAR(8))])
+    DruidFilter(condition=[SEARCH($2, Sarg['Aarhus':VARCHAR, 'New York':VARCHAR]:VARCHAR)])
       DruidTableScan(table=[[druid, wikipedia]], druid=[logical])
 
 !druidPlan