diff --git a/headers/private/kernel/disk_device_manager/KPartition.h b/headers/private/kernel/disk_device_manager/KPartition.h
index 7ff04da774..577d23a893 100644
--- a/headers/private/kernel/disk_device_manager/KPartition.h
+++ b/headers/private/kernel/disk_device_manager/KPartition.h
@@ -85,6 +85,7 @@ public:
 	bool ContainsPartitioningSystem() const;
 	bool IsReadOnly() const;
 	bool IsMounted() const;
+	bool IsChildMounted();
 
 	bool IsDevice() const;
 
diff --git a/src/system/kernel/disk_device_manager/KPartition.cpp b/src/system/kernel/disk_device_manager/KPartition.cpp
index 878ab99a79..cfe4263c3a 100644
--- a/src/system/kernel/disk_device_manager/KPartition.cpp
+++ b/src/system/kernel/disk_device_manager/KPartition.cpp
@@ -559,6 +559,20 @@ KPartition::IsMounted() const
 }
 
 
+bool
+KPartition::IsChildMounted()
+{
+	struct IsMountedVisitor : KPartitionVisitor {
+		virtual bool VisitPre(KPartition* partition)
+		{
+			return partition->IsMounted();
+		}
+	} checkVisitor;
+
+	return VisitEachDescendant(&checkVisitor) != NULL;
+}
+
+
 bool
 KPartition::IsDevice() const
 {
diff --git a/src/system/kernel/disk_device_manager/ddm_userland_interface.cpp b/src/system/kernel/disk_device_manager/ddm_userland_interface.cpp
index cadb0bd0b4..c445ea8b05 100644
--- a/src/system/kernel/disk_device_manager/ddm_userland_interface.cpp
+++ b/src/system/kernel/disk_device_manager/ddm_userland_interface.cpp
@@ -1249,7 +1249,8 @@ _user_uninitialize_partition(partition_id partitionID, int32* _changeCounter)
 	if (!partition->CheckAndMarkBusy(true))
 		return B_BUSY;
 
-	// TODO: We should also check, if any partition is mounted!
+	if (partition->IsMounted() || partition->IsChildMounted())
+		return B_BAD_DATA;
 
 	KDiskSystem* diskSystem = partition->DiskSystem();