diff --git a/symja_android_library/matheclipse-core/src/main/java/org/matheclipse/core/builtin/ListFunctions.java b/symja_android_library/matheclipse-core/src/main/java/org/matheclipse/core/builtin/ListFunctions.java
index 09a3529e1f..78df0f15fe 100644
--- a/symja_android_library/matheclipse-core/src/main/java/org/matheclipse/core/builtin/ListFunctions.java
+++ b/symja_android_library/matheclipse-core/src/main/java/org/matheclipse/core/builtin/ListFunctions.java
@@ -6192,22 +6192,24 @@ public IExpr evaluate(IAST ast, int argSize, IExpr[] option, EvalEngine engine,
         }
       }
       if (argSize == 3) {
-        IExpr arg3 = ast.arg3();
-        if (arg3.isList()) {
-          if (arg3.exists(x -> !x.isInteger())) {
+        IExpr lhs = ast.arg3(); 
+        IExpr rhs = ast.arg2();
+        if (lhs.isList()) {
+          if (lhs.exists(x -> !x.isInteger())) {
             // Position specification `1` in `2` is not a machine sized integer or a list of
             // machine-sized integers.
             return Errors.printMessage(S.ReplacePart, "psl", F.List(F.C3, ast), engine);
           }
         } else {
-          int position = arg3.toIntDefault();
+          int position = lhs.toIntDefault();
           if (position == Integer.MIN_VALUE) {
             // Position specification `1` in `2` is not a machine sized integer or a list of
             // machine-sized integers.
             return Errors.printMessage(S.ReplacePart, "psl", F.List(F.C3, ast), engine);
           }
         }
-        return result.replacePart(F.Rule(arg3, ast.arg2()), heads).orElse(result);
+        // Note: Rubi uses this kind of rule:
+        return result.replacePart(lhs, rhs, heads).orElse(result);
       }
       if (ast.arg2().isRuleAST()) {
         return ast.arg1().replacePart((IAST) ast.arg2(), heads).orElse(ast.arg1());
diff --git a/symja_android_library/matheclipse-core/src/main/java/org/matheclipse/core/interfaces/IExpr.java b/symja_android_library/matheclipse-core/src/main/java/org/matheclipse/core/interfaces/IExpr.java
index ec8951d99c..4e54a9609d 100644
--- a/symja_android_library/matheclipse-core/src/main/java/org/matheclipse/core/interfaces/IExpr.java
+++ b/symja_android_library/matheclipse-core/src/main/java/org/matheclipse/core/interfaces/IExpr.java
@@ -6059,7 +6059,7 @@ default IExpr replaceAll(final Map<? extends IExpr, ? extends IExpr> map) {
   /**
    * Replace all subexpressions with the given rule set. A rule must contain the position of the
    * subexpression which should be replaced on the left-hand-side. If no substitution matches, the
-   * method returns <code>F.NIL</code>.
+   * method returns {@link F#NIL}.
    *
    * @param astRules rules of the form <code>position-&gt;y</code> or <code>
    *     {position1-&gt;b, position2-&gt;d}</code>
@@ -6078,6 +6078,28 @@ default IExpr replacePart(final IAST astRules, IExpr.COMPARE_TERNARY heads) {
     return F.NIL;
   }
 
+  /**
+   * All subexpressions whose positions matches the left-hand-side (<code>lhs</code>) are replaced
+   * with the right-hand-side (<code>rhs</code>). If no substitution matches, the method returns
+   * {@link F#NIL}.
+   * 
+   * @param lhs the left-hand-side of the rule
+   * @param rhs the right-hand-side of the rule
+   * @param heads if <code>TRUE</code> also replace the heads of expressions
+   * @return
+   */
+  default IExpr replacePart(final IExpr lhs, IExpr rhs, IExpr.COMPARE_TERNARY heads) {
+    try {
+      return this.accept(new VisitorReplacePart(lhs, rhs, heads));
+    } catch (RuntimeException rex) {
+      Errors.rethrowsInterruptException(rex);
+      if (Config.SHOW_STACKTRACE) {
+        rex.printStackTrace();
+      }
+    }
+    return F.NIL;
+  }
+
   /**
    * Repeatedly replace all (sub-) expressions with the given unary function. If no substitution
    * matches, the method returns <code>this</code>.
diff --git a/symja_android_library/matheclipse-core/src/main/java/org/matheclipse/core/visit/VisitorReplacePart.java b/symja_android_library/matheclipse-core/src/main/java/org/matheclipse/core/visit/VisitorReplacePart.java
index c5c0282838..68318e6a1c 100644
--- a/symja_android_library/matheclipse-core/src/main/java/org/matheclipse/core/visit/VisitorReplacePart.java
+++ b/symja_android_library/matheclipse-core/src/main/java/org/matheclipse/core/visit/VisitorReplacePart.java
@@ -27,7 +27,7 @@ public class VisitorReplacePart extends AbstractVisitor {
    * <code>0</code> or <code>1</code>, depending if option <code>Heads->True</code> is set or the
    * <code>0</code> index position is used in the left-hand-side of a rule.
    */
-  private int offset;
+  private int startOffset;
 
   /**
    * The current evaluation engine for this thread.
@@ -43,25 +43,50 @@ public class VisitorReplacePart extends AbstractVisitor {
   public VisitorReplacePart(IAST rule, IExpr.COMPARE_TERNARY heads) {
     super();
     engine = EvalEngine.get();
+    startOffset = heads == IExpr.COMPARE_TERNARY.TRUE ? 0 : 1;
     if (rule.isRuleAST()) {
       rule = F.list(rule);
     }
     if (rule.isListOfRules()) {
       IAST list = rule;
       this.patternMatcherList = new ArrayList<IPatternMatcher>(list.argSize() + 3);
-      offset = heads == IExpr.COMPARE_TERNARY.TRUE ? 0 : 1;
+
       for (int i = 1; i < list.size(); i++) {
         rule = (IAST) list.get(i);
-        initPatternMatcher(rule, heads);
+        initPatternMatcher(rule.arg1(), rule.arg2(), heads);
       }
       if (heads == COMPARE_TERNARY.FALSE) {
-        offset = 1;
+        // if set explicitly to FALSE, then startOffset is always 1, otherwise startOffset may be
+        // changed in initPatternMatcher()
+        startOffset = 1;
       }
     }
   }
 
-  private void initPatternMatcher(IAST rule, IExpr.COMPARE_TERNARY heads) {
-    IExpr fromPositions = rule.arg1();
+  public VisitorReplacePart(IExpr lhs, IExpr rhs, IExpr.COMPARE_TERNARY heads) {
+    super();
+    engine = EvalEngine.get();
+    this.patternMatcherList = new ArrayList<IPatternMatcher>(1);
+    startOffset = heads == IExpr.COMPARE_TERNARY.TRUE ? 0 : 1;
+    initPatternMatcher(lhs, rhs, heads);
+    if (heads == COMPARE_TERNARY.FALSE) {
+      startOffset = 1;
+    }
+  }
+
+  /**
+   * Initialize the pattern matcher. If the left-hand-side is a list of lists of integers, then the
+   * right-hand-side is matched against the positions in the list.
+   * <p>
+   * <b>Note</b>: the {@link #startOffset} is set to <code>0</code> if a position <code>0</code> is
+   * found.
+   * 
+   * @param lhs
+   * @param rhs
+   * @param heads
+   */
+  private void initPatternMatcher(IExpr lhs, IExpr rhs, IExpr.COMPARE_TERNARY heads) {
+    IExpr fromPositions = lhs;
     try {
       // try extracting an int[] array of expressions
       if (fromPositions.isList()) {
@@ -76,11 +101,11 @@ private void initPatternMatcher(IAST rule, IExpr.COMPARE_TERNARY heads) {
                 throw ReturnException.RETURN_FALSE;
               }
               if (positions[k - 1] == 0) {
-                offset = 0;
+                startOffset = 0;
               }
             }
             IPatternMatcher evalPatternMatcher =
-                engine.evalPatternMatcher(F.Sequence(positions), rule.arg2());
+                engine.evalPatternMatcher(F.Sequence(positions), rhs);
             this.patternMatcherList.add(evalPatternMatcher);
           }
         } else {
@@ -93,34 +118,33 @@ private void initPatternMatcher(IAST rule, IExpr.COMPARE_TERNARY heads) {
                 throw ReturnException.RETURN_FALSE;
               }
               if (positions[j - 1] == 0) {
-                offset = 0;
+                startOffset = 0;
               }
             }
             IPatternMatcher evalPatternMatcher =
-                engine.evalPatternMatcher(F.Sequence(positions), rule.arg2());
+                engine.evalPatternMatcher(F.Sequence(positions), rhs);
             this.patternMatcherList.add(evalPatternMatcher);
           }
         }
       } else {
-        int[] positions = new int[] {rule.arg1().toIntDefault()};
+        int[] positions = new int[] {lhs.toIntDefault()};
         if (positions[0] == Integer.MIN_VALUE) {
           throw ReturnException.RETURN_FALSE;
         }
         if (positions[0] == 0) {
-          offset = 0;
+          startOffset = 0;
         }
-        IPatternMatcher evalPatternMatcher =
-            engine.evalPatternMatcher(F.Sequence(positions), rule.arg2());
+        IPatternMatcher evalPatternMatcher = engine.evalPatternMatcher(F.Sequence(positions), rhs);
         this.patternMatcherList.add(evalPatternMatcher);
 
       }
     } catch (ReturnException rex) {
       if (fromPositions.isList()) {
         IAST list = ((IAST) fromPositions).apply(S.Sequence, 1);
-        IPatternMatcher evalPatternMatcher = engine.evalPatternMatcher(list, rule.arg2());
+        IPatternMatcher evalPatternMatcher = engine.evalPatternMatcher(list, rhs);
         this.patternMatcherList.add(evalPatternMatcher);
       } else {
-        IPatternMatcher evalPatternMatcher = engine.evalPatternMatcher(fromPositions, rule.arg2());
+        IPatternMatcher evalPatternMatcher = engine.evalPatternMatcher(fromPositions, rhs);
         this.patternMatcherList.add(evalPatternMatcher);
       }
     }
@@ -128,7 +152,7 @@ private void initPatternMatcher(IAST rule, IExpr.COMPARE_TERNARY heads) {
 
   private IExpr visitPatternIndexList(IAST ast, IASTAppendable positions) {
     IASTAppendable result = F.NIL;
-    for (int i = offset; i < ast.size(); i++) {
+    for (int i = startOffset; i < ast.size(); i++) {
       final IInteger position = F.ZZ(i);
       for (int j = 0; j < patternMatcherList.size(); j++) {
         IPatternMatcher matcher = patternMatcherList.get(j);