diff --git a/repos/base-hw/src/core/core_region_map.cc b/repos/base-hw/src/core/core_region_map.cc
index 8965688c8a..f56d302efb 100644
--- a/repos/base-hw/src/core/core_region_map.cc
+++ b/repos/base-hw/src/core/core_region_map.cc
@@ -82,4 +82,11 @@ Core_region_map::attach(Dataspace_capability ds_cap, Attr const &attr)
 }
 
 
-void Core_region_map::detach(addr_t) { }
+void Core_region_map::detach(addr_t core_local_addr)
+{
+	size_t size = platform_specific().region_alloc_size_at((void *)core_local_addr);
+
+	unmap_local(core_local_addr, size >> get_page_size_log2());
+
+	platform().region_alloc().free((void *)core_local_addr);
+}
diff --git a/repos/base-hw/src/core/platform.h b/repos/base-hw/src/core/platform.h
index de24fa5150..62fd61469e 100644
--- a/repos/base-hw/src/core/platform.h
+++ b/repos/base-hw/src/core/platform.h
@@ -119,6 +119,18 @@ class Core::Platform : public Platform_generic
 		static addr_t                      core_page_table();
 		static Hw::Page_table::Allocator & core_page_table_allocator();
 
+		/**
+		 * Determine size of a core local mapping required for a
+		 * Core_region_map::detach().
+		 */
+		size_t region_alloc_size_at(void * addr)
+		{
+			using Size_at_error = Allocator_avl::Size_at_error;
+
+			return (_core_mem_alloc.virt_alloc())()->size_at(addr).convert<size_t>(
+				[ ] (size_t s)      { return s;  },
+				[ ] (Size_at_error) { return 0U; });
+		}
 
 		/********************************
 		 ** Platform_generic interface **