diff --git a/service/test/agama/storage/config_conversions/from_json_test.rb b/service/test/agama/storage/config_conversions/from_json_test.rb
index cfe4f508bc..b75af5aa5b 100644
--- a/service/test/agama/storage/config_conversions/from_json_test.rb
+++ b/service/test/agama/storage/config_conversions/from_json_test.rb
@@ -26,6 +26,9 @@
 require "y2storage/filesystems/mount_by_type"
 require "y2storage/filesystems/type"
 require "y2storage/pbkd_function"
+require "y2storage/refinements"
+
+using Y2Storage::Refinements::SizeCasts
 
 describe Agama::Storage::ConfigConversions::FromJSON do
   subject { described_class.new(config_json, product_config: product_config) }
@@ -73,6 +76,82 @@
     }
   end
 
+  shared_examples "omitting sizes" do |result|
+    let(:example_configs) do
+      [
+        { filesystem: { path: "/", type: { btrfs: { snapshots: false } } } },
+        { filesystem: { path: "/home" } },
+        { filesystem: { path: "/opt" } },
+        { filesystem: { path: "swap" } }
+      ]
+    end
+
+    it "uses default sizes" do
+      config = subject.convert
+      devices = result.call(config)
+      expect(devices).to contain_exactly(
+        an_object_having_attributes(
+          filesystem: have_attributes(path: "/"),
+          size:       have_attributes(default: true, min: be_nil, max: be_nil)
+        ),
+        an_object_having_attributes(
+          filesystem: have_attributes(path: "/home"),
+          size:       have_attributes(default: true, min: be_nil, max: be_nil)
+        ),
+        an_object_having_attributes(
+          filesystem: have_attributes(path: "/opt"),
+          size:       have_attributes(default: true, min: be_nil, max: be_nil)
+        ),
+        an_object_having_attributes(
+          filesystem: have_attributes(path: "swap"),
+          size:       have_attributes(default: true, min: be_nil, max: be_nil)
+        )
+      )
+    end
+  end
+
+  shared_examples "fixed sizes" do |result|
+    let(:example_configs) do
+      [
+        { filesystem: { path: "/" }, size: "10 GiB" },
+        { filesystem: { path: "/home" }, size: "6Gb" },
+        { filesystem: { path: "/opt" }, size: 3221225472 },
+        { filesystem: { path: "swap" }, size: "6 Gib" }
+      ]
+    end
+
+    it "sets both min and max to the same value if a string is used" do
+      config = subject.convert
+      devices = result.call(config)
+      expect(devices).to include(
+        an_object_having_attributes(
+          filesystem: have_attributes(path: "/"),
+          size:       have_attributes(default: false, min: 10.GiB, max: 10.GiB)
+        )
+      )
+    end
+
+    it "sets both min and max to the same value if an integer is used" do
+      config = subject.convert
+      devices = result.call(config)
+      expect(devices).to include(
+        an_object_having_attributes(
+          filesystem: have_attributes(path: "/opt"),
+          size:       have_attributes(default: false, min: 3.GiB, max: 3.GiB)
+        )
+      )
+    end
+
+    it "makes a difference between SI units and binary units" do
+      config = subject.convert
+      devices = result.call(config)
+      home_size = devices.find { |d| d.filesystem.path == "/home" }.size
+      swap_size = devices.find { |d| d.filesystem.path == "swap" }.size
+      expect(swap_size.min.to_i).to eq 6 * 1024 * 1024 * 1024
+      expect(home_size.max.to_i).to eq 6 * 1000 * 1000 * 1000
+    end
+  end
+
   before do
     # Speed up tests by avoding real check of TPM presence.
     allow(Y2Storage::EncryptionMethod::TPM_FDE).to receive(:possible?).and_return(true)
@@ -439,43 +518,15 @@
         {
           drives: [
             {
-              partitions: [
-                { filesystem: { path: "/", type: { btrfs: { snapshots: false } } } },
-                { filesystem: { path: "/home" } },
-                { filesystem: { path: "/opt" } },
-                { filesystem: { path: "swap" } }
-              ]
+              partitions: example_configs
             }
           ]
         }
       end
 
-      it "uses default sizes" do
-        config = subject.convert
-        partitions = config.drives.first.partitions
-        expect(partitions).to contain_exactly(
-          an_object_having_attributes(
-            filesystem: have_attributes(path: "/"),
-            size:       have_attributes(default: true, min: 5.GiB, max: 10.GiB)
-          ),
-          an_object_having_attributes(
-            filesystem: have_attributes(path: "/home"),
-            size:       have_attributes(default: true, min: 5.GiB,
-              max: Y2Storage::DiskSize.unlimited)
-          ),
-          an_object_having_attributes(
-            filesystem: have_attributes(path: "/opt"),
-            size:       have_attributes(default: true, min: 100.MiB,
-              max: Y2Storage::DiskSize.unlimited)
-          ),
-          an_object_having_attributes(
-            filesystem: have_attributes(path: "swap"),
-            size:       have_attributes(
-              default: true, min: Y2Storage::DiskSize.zero, max: Y2Storage::DiskSize.unlimited
-            )
-          )
-        )
-      end
+      result = proc { |config| config.drives.first.partitions }
+
+      include_examples "omitting sizes", result
     end
 
     context "setting fixed sizes for the partitions" do
@@ -483,47 +534,15 @@
         {
           drives: [
             {
-              partitions: [
-                { filesystem: { path: "/" }, size: "10 GiB" },
-                { filesystem: { path: "/home" }, size: "6Gb" },
-                { filesystem: { path: "/opt" }, size: 3221225472 },
-                { filesystem: { path: "swap" }, size: "6 Gib" }
-              ]
+              partitions: example_configs
             }
           ]
         }
       end
 
-      it "sets both min and max to the same value if a string is used" do
-        config = subject.convert
-        partitions = config.drives.first.partitions
-        expect(partitions).to include(
-          an_object_having_attributes(
-            filesystem: have_attributes(path: "/"),
-            size:       have_attributes(default: false, min: 10.GiB, max: 10.GiB)
-          )
-        )
-      end
-
-      it "sets both min and max to the same value if an integer is used" do
-        config = subject.convert
-        partitions = config.drives.first.partitions
-        expect(partitions).to include(
-          an_object_having_attributes(
-            filesystem: have_attributes(path: "/opt"),
-            size:       have_attributes(default: false, min: 3.GiB, max: 3.GiB)
-          )
-        )
-      end
+      result = proc { |config| config.drives.first.partitions }
 
-      it "makes a difference between SI units and binary units" do
-        config = subject.convert
-        partitions = config.drives.first.partitions
-        home_size = partitions.find { |p| p.filesystem.path == "/home" }.size
-        swap_size = partitions.find { |p| p.filesystem.path == "swap" }.size
-        expect(swap_size.min.to_i).to eq 6 * 1024 * 1024 * 1024
-        expect(home_size.max.to_i).to eq 6 * 1000 * 1000 * 1000
-      end
+      include_examples "fixed sizes", result
     end
 
     # Note the min is mandatory
@@ -575,6 +594,29 @@
             )
           )
         end
+
+        it "uses nil for min size as current" do
+          config = subject.convert
+          partitions = config.drives.first.partitions
+          expect(partitions).to include(
+            an_object_having_attributes(
+              filesystem: have_attributes(path: "/data1"),
+              size:       have_attributes(default: false, min: be_nil,
+                max: Y2Storage::DiskSize.unlimited)
+            )
+          )
+        end
+
+        it "uses nil for max size as current" do
+          config = subject.convert
+          partitions = config.drives.first.partitions
+          expect(partitions).to include(
+            an_object_having_attributes(
+              filesystem: have_attributes(path: "/data2"),
+              size:       have_attributes(default: false, min: 10.GiB, max: be_nil)
+            )
+          )
+        end
       end
 
       context "using a hash" do
@@ -598,6 +640,14 @@
                   {
                     filesystem: { path: "/opt" },
                     size:       { min: "1073741824", max: 3221225472 }
+                  },
+                  {
+                    filesystem: { path: "/data1" },
+                    size:       { min: "current" }
+                  },
+                  {
+                    filesystem: { path: "/data2" },
+                    size:       { min: "10 GiB", max: "current" }
                   }
                 ]
               }
@@ -629,6 +679,14 @@
                   {
                     filesystem: { path: "/opt" },
                     size:       ["1073741824", 3221225472]
+                  },
+                  {
+                    filesystem: { path: "/data1" },
+                    size:       ["current"]
+                  },
+                  {
+                    filesystem: { path: "/data2" },
+                    size:       ["10 GiB", "current"]
                   }
                 ]
               }
@@ -958,8 +1016,8 @@
             ),
             size:        have_attributes(
               default: true,
-              min:     40.GiB,
-              max:     Y2Storage::DiskSize.unlimited
+              min:     be_nil,
+              max:     be_nil
             ),
             stripes:     be_nil,
             stripe_size: be_nil,
@@ -1004,5 +1062,21 @@
         )
       end
     end
+
+    context "omitting sizes for the logical volumes" do
+      let(:config_json) do
+        {
+          volumeGroups: [
+            {
+              logicalVolumes: example_configs
+            }
+          ]
+        }
+      end
+
+      result = proc { |config| config.volume_groups.first.logical_volumes }
+
+      include_examples "omitting sizes", result
+    end
   end
 end