diff --git a/browser/css/spreadsheet.css b/browser/css/spreadsheet.css
index 6cfb0865d7..55176635e7 100644
--- a/browser/css/spreadsheet.css
+++ b/browser/css/spreadsheet.css
@@ -25,7 +25,8 @@
 	text-decoration: none;
 
 	font: var(--default-font-size)/1.5 var(--cool-font);
-	display: inline-block;
+	display: inline-grid;
+	grid-auto-flow: column;
 	border: 1px solid transparent;
 	border-radius: var(--border-radius);
 	background: var(--color-main-background);
@@ -38,6 +39,13 @@
 	border: 1px solid var(--color-border-dark);
 }
 
+.spreadsheet-tab.spreadsheet-tab-protected > .lock, .spreadsheet-tab.spreadsheet-tab-protected:hover > .lock {
+	width: 16px;
+	height: 16px;
+	background-image: url('images/lc_protect.svg') !important;
+	background-repeat: no-repeat !important;
+}
+
 #spreadsheet-tab-scroll button.spreadsheet-tab-selected:hover {
 	background-color: var(--color-primary-dark) !important;
 	color: var(--color-primary-text) !important;
diff --git a/browser/src/control/Control.Tabs.js b/browser/src/control/Control.Tabs.js
index 05d312dd07..b63d6ce395 100644
--- a/browser/src/control/Control.Tabs.js
+++ b/browser/src/control/Control.Tabs.js
@@ -203,6 +203,8 @@ L.Control.Tabs = L.Control.extend({
 					dropZoneIndicator.id = 'drop-zone-' + i;
 					var id = 'spreadsheet-tab' + i;
 					var tab = L.DomUtil.create('button', 'spreadsheet-tab', ssTabScroll);
+					L.DomUtil.create('div', 'lock', tab);
+					let label = L.DomUtil.create('div', '', tab);
 					if (window.mode.isMobile() || window.mode.isTablet()) {
 						(new Hammer(tab, {recognizers: [[Hammer.Press]]}))
 							.on('press', function (j) {
@@ -239,7 +241,13 @@ L.Control.Tabs = L.Control.extend({
 						}(i).bind(this));
 					}
 
-					tab.textContent = e.partNames[i];
+					if (e.protectedParts[i]) {
+						L.DomUtil.addClass(tab, 'spreadsheet-tab-protected');
+					}
+					else {
+						L.DomUtil.removeClass(tab, 'spreadsheet-tab-protected');
+					}
+					label.textContent = e.partNames[i];
 					tab.id = id;
 
 					L.DomEvent
@@ -311,7 +319,7 @@ L.Control.Tabs = L.Control.extend({
 	},
 
 	_setPart: function (e) {
-		var part =  e.target.id.match(/\d+/g)[0];
+		var part =  e.currentTarget.id.match(/\d+/g)[0];
 		if (part !== null) {
 			this._setPartIndex(parseInt(part));
 		}
diff --git a/browser/src/core/Socket.js b/browser/src/core/Socket.js
index 869ad63c84..994bbada67 100644
--- a/browser/src/core/Socket.js
+++ b/browser/src/core/Socket.js
@@ -1760,6 +1760,13 @@ app.definitions.Socket = L.Class.extend({
 					command.rtlParts.push(parseInt(item));
 				});
 			}
+			else if (tokens[i].startsWith('protectedparts=')) {
+				let protectedParts = tokens[i].substring(15).split(',');
+				command.protectedParts = [];
+				protectedParts.forEach(function (item) {
+					command.protectedParts.push(parseInt(item));
+				});
+			}
 			else if (tokens[i].startsWith('hash=')) {
 				command.hash = tokens[i].substring('hash='.length);
 			}
diff --git a/browser/src/layer/tile/CalcTileLayer.js b/browser/src/layer/tile/CalcTileLayer.js
index 3f10dd044b..43a668f21e 100644
--- a/browser/src/layer/tile/CalcTileLayer.js
+++ b/browser/src/layer/tile/CalcTileLayer.js
@@ -430,6 +430,14 @@ L.CalcTileLayer = L.CanvasTileLayer.extend({
 				this._updateMaxBounds(true);
 			}
 			this._hiddenParts = command.hiddenparts || [];
+
+			let pparts = [];
+			pparts.length = command.parts;
+			this._protectedParts = pparts.fill(false, 0, command.parts);
+			if (command.protectedParts) {
+				command.protectedParts.forEach(i => this._protectedParts[i] = true);
+			}
+
 			this._handleRTLFlags(command);
 			this._documentInfo = textMsg;
 			var partNames = textMsg.match(/[^\r\n]+/g);
@@ -441,6 +449,7 @@ L.CalcTileLayer = L.CanvasTileLayer.extend({
 				docType: this._docType,
 				partNames: this._partNames,
 				hiddenParts: this._hiddenParts,
+				protectedParts: this._protectedParts,
 				source: 'status'
 			});
 			this._resetPreFetching(true);
diff --git a/kit/KitHelper.hpp b/kit/KitHelper.hpp
index e2f987daa7..0b86c08cbd 100644
--- a/kit/KitHelper.hpp
+++ b/kit/KitHelper.hpp
@@ -14,6 +14,7 @@
 #include <sstream>
 #include <string>
 
+#include <JsonUtil.hpp>
 #include <Util.hpp>
 
 #define LOK_USE_UNSTABLE_API
@@ -79,6 +80,7 @@ namespace LOKitHelper
             std::ostringstream hposs;
             std::ostringstream sposs;
             std::ostringstream rtlposs;
+            std::ostringstream protectss;
             std::string mode;
             for (int i = 0; i < parts; ++i)
             {
@@ -103,6 +105,11 @@ namespace LOKitHelper
                         if (prop.second == "1")
                             rtlposs << i << ',';
                     }
+                    else if (name == "protected")
+                    {
+                        if (prop.second == "1")
+                            protectss << i << ',';
+                    }
                     else if (name == "mode" && mode.empty())
                     {
                         std::ostringstream modess;
@@ -136,6 +143,13 @@ namespace LOKitHelper
                 oss << " rtlparts=" << rtlparts;
             }
 
+            std::string protectparts = protectss.str();
+            if (!protectparts.empty())
+            {
+                protectparts.pop_back(); // Remove last ','
+                oss << " protectedparts=" << protectparts;
+            }
+
             if (type == LOK_DOCTYPE_SPREADSHEET)
             {
                 char* values = loKitDocument->pClass->getCommandValues(loKitDocument, ".uno:ReadOnly");