diff --git a/core/api/core.api b/core/api/core.api
index fa71b6b95a..0779a80814 100644
--- a/core/api/core.api
+++ b/core/api/core.api
@@ -9544,11 +9544,6 @@ public final class org/jetbrains/kotlinx/dataframe/columns/SingleColumn$DefaultI
 	public static fun resolve (Lorg/jetbrains/kotlinx/dataframe/columns/SingleColumn;Lorg/jetbrains/kotlinx/dataframe/columns/ColumnResolutionContext;)Ljava/util/List;
 }
 
-public final class org/jetbrains/kotlinx/dataframe/columns/SingleColumnKt {
-	public static final fun isSingleColumn (Lorg/jetbrains/kotlinx/dataframe/columns/ColumnsResolver;)Z
-	public static final fun isSingleColumnWithGroup (Lorg/jetbrains/kotlinx/dataframe/columns/ColumnsResolver;Ljava/util/List;)Z
-}
-
 public abstract interface class org/jetbrains/kotlinx/dataframe/columns/TypeSuggestion {
 	public static final field Companion Lorg/jetbrains/kotlinx/dataframe/columns/TypeSuggestion$Companion;
 }
diff --git a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/all.kt b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/all.kt
index a85ddbeb99..2e64efff84 100644
--- a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/all.kt
+++ b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/api/all.kt
@@ -17,7 +17,6 @@ import org.jetbrains.kotlinx.dataframe.columns.ColumnSet
 import org.jetbrains.kotlinx.dataframe.columns.ColumnWithPath
 import org.jetbrains.kotlinx.dataframe.columns.ColumnsResolver
 import org.jetbrains.kotlinx.dataframe.columns.SingleColumn
-import org.jetbrains.kotlinx.dataframe.columns.isSingleColumnWithGroup
 import org.jetbrains.kotlinx.dataframe.columns.size
 import org.jetbrains.kotlinx.dataframe.columns.values
 import org.jetbrains.kotlinx.dataframe.documentation.AccessApiLink
@@ -1163,14 +1162,16 @@ public interface AllColumnsSelectionDsl<out _UNUSED> {
 }
 
 /**
- * If [this] is a [SingleColumn] containing a single [ColumnGroup], it
+ * If [this] is a [SingleColumn] containing a single [ColumnGroup]
+ * (like [SingleColumn][SingleColumn]`<`[AnyRow][AnyRow]`>` or [ColumnsSelectionDsl][ColumnsSelectionDsl]), it
  * returns a [(transformable) ColumnSet][TransformableColumnSet] containing the children of this [ColumnGroup],
- * else it simply returns a [(transformable) ColumnSet][TransformableColumnSet] from [this].
+ * else it simply returns a [(transformable) ColumnSet][TransformableColumnSet] from [this]
+ * (like when [this] is a [ColumnSet]).
  */
 internal fun ColumnsResolver<*>.allColumnsInternal(removePaths: Boolean = false): TransformableColumnSet<*> =
-    transform {
-        if (isSingleColumnWithGroup(it)) {
-            it.single().let {
+    transform { cols ->
+        if (this is SingleColumn<*> && cols.singleOrNull()?.isColumnGroup() == true) {
+            cols.single().let {
                 if (removePaths) {
                     it.asColumnGroup().columns().map(AnyCol::addPath)
                 } else {
@@ -1178,7 +1179,7 @@ internal fun ColumnsResolver<*>.allColumnsInternal(removePaths: Boolean = false)
                 }
             }
         } else {
-            it
+            cols
         }
     }
 
diff --git a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/columns/SingleColumn.kt b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/columns/SingleColumn.kt
index e8d0e048be..b422c5414f 100644
--- a/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/columns/SingleColumn.kt
+++ b/core/src/main/kotlin/org/jetbrains/kotlinx/dataframe/columns/SingleColumn.kt
@@ -1,7 +1,6 @@
 package org.jetbrains.kotlinx.dataframe.columns
 
 import org.jetbrains.kotlinx.dataframe.DataColumn
-import org.jetbrains.kotlinx.dataframe.api.isColumnGroup
 import org.jetbrains.kotlinx.dataframe.impl.columns.TransformableColumnSet
 import org.jetbrains.kotlinx.dataframe.impl.columns.TransformableSingleColumn
 
@@ -23,11 +22,3 @@ public interface SingleColumn<out C> : ColumnsResolver<C> {
 
     public fun resolveSingle(context: ColumnResolutionContext): ColumnWithPath<C>?
 }
-
-public fun ColumnsResolver<*>.isSingleColumn(): Boolean = this is SingleColumn<*>
-
-/**
- * Returns true if [this] is a [SingleColumn] and [cols] consists of a single column group.
- */
-public fun ColumnsResolver<*>.isSingleColumnWithGroup(cols: List<ColumnWithPath<*>>): Boolean =
-    isSingleColumn() && cols.singleOrNull()?.isColumnGroup() == true
diff --git a/core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/api/colsAtAnyDepth.kt b/core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/api/colsAtAnyDepth.kt
index fa5adc5969..30160ff9b5 100644
--- a/core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/api/colsAtAnyDepth.kt
+++ b/core/src/test/kotlin/org/jetbrains/kotlinx/dataframe/api/colsAtAnyDepth.kt
@@ -13,10 +13,14 @@ import org.jetbrains.kotlinx.dataframe.impl.columns.transform
 import org.jetbrains.kotlinx.dataframe.impl.columns.tree.flattenRecursively
 import org.jetbrains.kotlinx.dataframe.kind
 import org.jetbrains.kotlinx.dataframe.samples.api.TestBase
+import org.jetbrains.kotlinx.dataframe.samples.api.age
 import org.jetbrains.kotlinx.dataframe.samples.api.city
 import org.jetbrains.kotlinx.dataframe.samples.api.firstName
 import org.jetbrains.kotlinx.dataframe.samples.api.lastName
 import org.jetbrains.kotlinx.dataframe.samples.api.name
+import org.jetbrains.kotlinx.dataframe.samples.api.secondName
+import org.jetbrains.kotlinx.dataframe.samples.api.thirdName
+import org.jetbrains.kotlinx.dataframe.samples.api.weight
 import org.junit.Test
 import kotlin.reflect.typeOf
 
@@ -153,17 +157,15 @@ class AtAnyDepth : TestBase() {
             dfWithFrames.getColumnsWithPaths { name[frameCol] and frameCol }
     }
 
-    //    @Test
+    @Test
     fun `cols of kind atAnyDepth`() {
         listOf(
             dfGroup.getColumnsWithPaths {
                 colsAtAnyDepth().colsOfKind(Frame, Value) { "e" in it.name }
             },
             dfGroup.getColumnsWithPaths {
-                asSingleColumn().ensureIsColumnGroup().asColumnSet().dfsInternal { "e" in it.name }
+                name { firstName.allCols() and lastName } and cols(age, weight)
             },
-        ).map {
-            it.sortedBy { it.name }.map { it.name to it.path }
-        }.shouldAllBeEqual()
+        ).map { it.map { it.path.joinToString() } }.shouldAllBeEqual()
     }
 }