diff --git a/data.cpp b/data.cpp
index 088dbda..b1e8404 100755
--- a/data.cpp
+++ b/data.cpp
@@ -783,6 +783,7 @@
 #else
 	mPersist.SetValue(TW_NO_SHA2, "1");
 #endif
+	mPersist.SetValue(TW_UNMOUNT_SYSTEM, "1");
 
 #ifdef TW_NO_SCREEN_TIMEOUT
 	mConst.SetValue("tw_screen_timeout_secs", "0");
diff --git a/gui/theme/common/landscape.xml b/gui/theme/common/landscape.xml
index 8244c46..230b72f 100755
--- a/gui/theme/common/landscape.xml
+++ b/gui/theme/common/landscape.xml
@@ -2937,6 +2937,9 @@
 					<condition var1="tw_no_sha2" var2="0"/>
 					<data variable="tw_use_sha2"/>
 				</listitem>
+				<listitem name="{@unmount_sys_install=Unmount System before installing a ZIP}">
+					<data variable="tw_unmount_system"/>
+				</listitem>
 			</listbox>
 
 			<checkbox>
diff --git a/gui/theme/common/languages/en.xml b/gui/theme/common/languages/en.xml
index 4a0ac7f..3769da5 100755
--- a/gui/theme/common/languages/en.xml
+++ b/gui/theme/common/languages/en.xml
@@ -719,5 +719,8 @@
 		<string name="include_kernel_log">Include Kernel Log</string>
 		<string name="sha2_chk">Use SHA2 for hashing</string>
 		<string name="unable_set_boot_slot">Error changing bootloader boot slot to {1}</string>
+		<string name="unmount_sys_install">Unmount System before installing a ZIP</string>
+		<string name="unmount_system">Unmounting System...</string>
+		<string name="unmount_system_err">Failed unmounting System</string>
 	</resources>
 </language>
diff --git a/gui/theme/common/portrait.xml b/gui/theme/common/portrait.xml
index e014cc5..8370414 100755
--- a/gui/theme/common/portrait.xml
+++ b/gui/theme/common/portrait.xml
@@ -3150,6 +3150,9 @@
 					<condition var1="tw_no_sha2" var2="0"/>
 					<data variable="tw_use_sha2"/>
 				</listitem>
+				<listitem name="{@unmount_sys_install=Unmount System before installing a ZIP}">
+					<data variable="tw_unmount_system"/>
+				</listitem>
 			</listbox>
 
 			<button style="main_button_half_height">
diff --git a/gui/theme/common/watch.xml b/gui/theme/common/watch.xml
index f5d3222..05b7bd2 100755
--- a/gui/theme/common/watch.xml
+++ b/gui/theme/common/watch.xml
@@ -3640,6 +3640,9 @@
 					<condition var1="tw_no_sha2" var2="0"/>
 					<data variable="tw_use_sha2"/>
 				</listitem>
+				<listitem name="{@unmount_sys_install=Unmount System before installing a ZIP}">
+					<data variable="tw_unmount_system"/>
+				</listitem>
 			</listbox>
 
 			<action>
diff --git a/twinstall.cpp b/twinstall.cpp
index d659b47..92af497 100755
--- a/twinstall.cpp
+++ b/twinstall.cpp
@@ -339,7 +339,7 @@
 }
 
 int TWinstall_zip(const char* path, int* wipe_cache) {
-	int ret_val, zip_verify = 1;
+	int ret_val, zip_verify = 1, unmount_system = 1;
 
 	if (strcmp(path, "error") == 0) {
 		LOGERR("Failed to get adb sideload file: '%s'\n", path);
@@ -359,6 +359,8 @@
 		}
 	}
 
+	DataManager::GetValue(TW_UNMOUNT_SYSTEM, unmount_system);
+
 #ifndef TW_OEM_BUILD
 	DataManager::GetValue(TW_SIGNED_ZIP_VERIFY_VAR, zip_verify);
 #endif
@@ -410,6 +412,14 @@
 		return INSTALL_CORRUPT;
 	}
 
+	if (unmount_system) {
+		gui_msg("unmount_system=Unmounting System...");
+		if(!PartitionManager.UnMount_By_Path(PartitionManager.Get_Android_Root_Path(), true)) {
+			gui_err("unmount_system_err=Failed unmounting System");
+			return -1;
+		}
+	}
+
 	time_t start, stop;
 	time(&start);
 	if (Zip.EntryExists(ASSUMED_UPDATE_BINARY_NAME)) {
diff --git a/variables.h b/variables.h
index 76da715..24cde92 100644
--- a/variables.h
+++ b/variables.h
@@ -140,6 +140,7 @@
 #define TW_MILITARY_TIME            "tw_military_time"
 #define TW_USE_SHA2                 "tw_use_sha2"
 #define TW_NO_SHA2                  "tw_no_sha2"
+#define TW_UNMOUNT_SYSTEM           "tw_unmount_system"
 
 // Also used:
 //   tw_boot_is_mountable