diff --git a/eo-runtime/src/main/java/org/eolang/AtComposite.java b/eo-runtime/src/main/java/org/eolang/AtComposite.java
index 12f1d4237e..f71b273363 100644
--- a/eo-runtime/src/main/java/org/eolang/AtComposite.java
+++ b/eo-runtime/src/main/java/org/eolang/AtComposite.java
@@ -65,7 +65,7 @@ public Phi get() {
     }
 
     @Override
-    public void put(final Phi phi) {
+    public void put(final int pos, final Phi phi) {
         throw new ExReadOnly(
             "Can't overwrite lambda expression"
         );
diff --git a/eo-runtime/src/main/java/org/eolang/AtLogged.java b/eo-runtime/src/main/java/org/eolang/AtLogged.java
index 5e878b3a91..4dda88cfa9 100644
--- a/eo-runtime/src/main/java/org/eolang/AtLogged.java
+++ b/eo-runtime/src/main/java/org/eolang/AtLogged.java
@@ -87,9 +87,9 @@ public Phi get() {
     }
 
     @Override
-    public void put(final Phi src) {
+    public void put(final int pos, final Phi src) {
         this.log.info(String.format("  %s.put()...\n", this.owner));
-        this.origin.put(src);
+        this.origin.put(pos, src);
         this.log.info(String.format("  %s.put()!\n", this.owner));
     }
 }
diff --git a/eo-runtime/src/main/java/org/eolang/AtOnce.java b/eo-runtime/src/main/java/org/eolang/AtOnce.java
index bc19bdc183..d130229aaf 100644
--- a/eo-runtime/src/main/java/org/eolang/AtOnce.java
+++ b/eo-runtime/src/main/java/org/eolang/AtOnce.java
@@ -70,7 +70,7 @@ public Phi get() {
     }
 
     @Override
-    public void put(final Phi phi) {
+    public void put(final int pos, final Phi phi) {
         throw new ExReadOnly(
             String.format(
                 "Can't overwrite the \"%s\" attribute",
diff --git a/eo-runtime/src/main/java/org/eolang/AtRho.java b/eo-runtime/src/main/java/org/eolang/AtRho.java
index 89a99de2ae..dbcf229c54 100644
--- a/eo-runtime/src/main/java/org/eolang/AtRho.java
+++ b/eo-runtime/src/main/java/org/eolang/AtRho.java
@@ -70,7 +70,7 @@ public Phi get() {
     }
 
     @Override
-    public void put(final Phi phi) {
+    public void put(final int pos, final Phi phi) {
         if (this.rho.get() == null) {
             this.rho.set(phi);
         }
diff --git a/eo-runtime/src/main/java/org/eolang/AtVoid.java b/eo-runtime/src/main/java/org/eolang/AtVoid.java
index 2a1ec38c25..4cf0ddc9ca 100644
--- a/eo-runtime/src/main/java/org/eolang/AtVoid.java
+++ b/eo-runtime/src/main/java/org/eolang/AtVoid.java
@@ -89,7 +89,7 @@ public Phi get() {
     }
 
     @Override
-    public void put(final Phi phi) {
+    public void put(final int pos, final Phi phi) {
         if (this.object.get() == null) {
             this.object.set(phi);
         } else {
diff --git a/eo-runtime/src/main/java/org/eolang/AtWithRho.java b/eo-runtime/src/main/java/org/eolang/AtWithRho.java
index bb25fffa51..1d9d50dae1 100644
--- a/eo-runtime/src/main/java/org/eolang/AtWithRho.java
+++ b/eo-runtime/src/main/java/org/eolang/AtWithRho.java
@@ -68,7 +68,7 @@ public Phi get() {
     }
 
     @Override
-    public void put(final Phi phi) {
-        this.origin.put(phi);
+    public void put(final int pos, final Phi phi) {
+        this.origin.put(pos, phi);
     }
 }
diff --git a/eo-runtime/src/main/java/org/eolang/Attr.java b/eo-runtime/src/main/java/org/eolang/Attr.java
index c1958c4074..a95969025d 100644
--- a/eo-runtime/src/main/java/org/eolang/Attr.java
+++ b/eo-runtime/src/main/java/org/eolang/Attr.java
@@ -65,7 +65,8 @@ public interface Attr {
     /**
      * Put a new object in.
      *
+     * @param pos The position
      * @param phi The object to put
      */
-    void put(Phi phi);
+    void put(int pos, Phi phi);
 }
diff --git a/eo-runtime/src/main/java/org/eolang/PhDefault.java b/eo-runtime/src/main/java/org/eolang/PhDefault.java
index 4de4f93877..f176a036da 100644
--- a/eo-runtime/src/main/java/org/eolang/PhDefault.java
+++ b/eo-runtime/src/main/java/org/eolang/PhDefault.java
@@ -140,11 +140,15 @@ public boolean hasRho() {
 
     @Override
     public void put(final int pos, final Phi object) {
-        this.put(this.attr(pos), object);
+        this.attrObject(this.attr(pos), object).put(pos, object);
     }
 
     @Override
     public void put(final String name, final Phi object) {
+        this.attrObject(name, object).put(0, object);
+    }
+
+    private Attr attrObject(final String name, final Phi object) {
         if (!this.attrs.containsKey(name)) {
             throw new ExUnset(
                 String.format(
@@ -153,7 +157,7 @@ public void put(final String name, final Phi object) {
                 )
             );
         }
-        this.attrs.get(name).put(object);
+        return this.attrs.get(name);
     }
 
     @Override
diff --git a/eo-runtime/src/test/java/org/eolang/AtEnvelope.java b/eo-runtime/src/test/java/org/eolang/AtEnvelope.java
index 6b28f01286..7d15ae8948 100644
--- a/eo-runtime/src/test/java/org/eolang/AtEnvelope.java
+++ b/eo-runtime/src/test/java/org/eolang/AtEnvelope.java
@@ -56,7 +56,7 @@ public Phi get() {
     }
 
     @Override
-    public void put(final Phi phi) {
-        this.origin.put(phi);
+    public void put(final int pos, final Phi phi) {
+        this.origin.put(pos, phi);
     }
 }
diff --git a/eo-runtime/src/test/java/org/eolang/PhDefaultTest.java b/eo-runtime/src/test/java/org/eolang/PhDefaultTest.java
index 1addd5b097..ba6686591e 100644
--- a/eo-runtime/src/test/java/org/eolang/PhDefaultTest.java
+++ b/eo-runtime/src/test/java/org/eolang/PhDefaultTest.java
@@ -23,6 +23,7 @@
  */
 package org.eolang;
 
+import EOorg.EOeolang.EOnumber;
 import com.yegor256.Together;
 import java.security.SecureRandom;
 import org.cactoos.set.SetOf;
@@ -488,6 +489,19 @@ void doesNotCalculateRandomTwice() {
         );
     }
 
+    @Test
+    void failsCorrectlyWhenTooManyAttributesPut() {
+        MatcherAssert.assertThat(
+            "the message explains what's going on",
+            Assertions.assertThrows(
+                ExAbstract.class,
+                () -> new EOnumber().put(1, new Data.ToPhi(1)),
+                "fails when trying to set attribute with too big position"
+            ).getMessage(),
+            Matchers.equalTo("There are no void attributes left, can't set the 1st one")
+        );
+    }
+    
     /**
      * Rnd.
      * @since 0.1.0