diff --git a/phpBB/adm/style/overall_header.html b/phpBB/adm/style/overall_header.html
index 0720519ce2..ccf38e49b8 100644
--- a/phpBB/adm/style/overall_header.html
+++ b/phpBB/adm/style/overall_header.html
@@ -28,9 +28,16 @@ function jumpto()
 {
 	var page = prompt(jump_page, on_page);
 
-	if (page !== null && !isNaN(page) && page > 0)	
+	if (page !== null && !isNaN(page) && page == Math.floor(page) && page > 0)
 	{
-		document.location.href = base_url.replace(/&/g, '&') + '&start=' + ((page - 1) * per_page);
+		if (base_url.indexOf('?') == -1)
+		{
+			document.location.href = base_url + '?start=' + ((page - 1) * per_page);
+		}
+		else
+		{
+			document.location.href = base_url.replace(/&/g, '&') + '&start=' + ((page - 1) * per_page);
+		}
 	}
 }
 
diff --git a/phpBB/adm/style/simple_header.html b/phpBB/adm/style/simple_header.html
index 3e36c47988..2339b70a93 100644
--- a/phpBB/adm/style/simple_header.html
+++ b/phpBB/adm/style/simple_header.html
@@ -39,9 +39,16 @@ function jumpto()
 {
 	var page = prompt(jump_page, on_page);
 
-	if (page !== null && !isNaN(page) && page > 0)	
+	if (page !== null && !isNaN(page) && page == Math.floor(page) && page > 0)
 	{
-		document.location.href = base_url.replace(/&/g, '&') + '&start=' + ((page - 1) * per_page);
+		if (base_url.indexOf('?') == -1)
+		{
+			document.location.href = base_url + '?start=' + ((page - 1) * per_page);
+		}
+		else
+		{
+			document.location.href = base_url.replace(/&/g, '&') + '&start=' + ((page - 1) * per_page);
+		}
 	}
 }
 
diff --git a/phpBB/docs/CHANGELOG.html b/phpBB/docs/CHANGELOG.html
index 875281d5d2..62c64a9c2a 100644
--- a/phpBB/docs/CHANGELOG.html
+++ b/phpBB/docs/CHANGELOG.html
@@ -150,6 +150,7 @@
 		<li>[Change] Add unique key to ACL options table to prevent duplicate permission options. (Bug #41835)</li>
 		<li>[Change] Redirect to relevant MCP page of multi-page topic if accessing quickmod tools (Split option for example)</li>
 		<li>[Change] Performance improvements for native fulltext search (patch by Paul)</li>
+		<li>[Change] Changed jumpto() JS function to be more fail-safe. (But #27635 - patch by peterkclee)</li>
 		<li>[Feature] Added new options for visual confirmation.</li>
 		<li>[Feature] Allow download of conflicting file for later reference in automatic updater</li>
 		<li>[Feature] Allow translation of custom BBCode help messages. (Patch by bantu)</li>
diff --git a/phpBB/styles/prosilver/template/forum_fn.js b/phpBB/styles/prosilver/template/forum_fn.js
index 6694dfb61b..06c4d1e785 100644
--- a/phpBB/styles/prosilver/template/forum_fn.js
+++ b/phpBB/styles/prosilver/template/forum_fn.js
@@ -23,9 +23,16 @@ function jumpto()
 {
 	var page = prompt(jump_page, on_page);
 
-	if (page !== null && !isNaN(page) && page > 0)
+	if (page !== null && !isNaN(page) && page == Math.floor(page) && page > 0)
 	{
-		document.location.href = base_url.replace(/&amp;/g, '&') + '&start=' + ((page - 1) * per_page);
+		if (base_url.indexOf('?') == -1)
+		{
+			document.location.href = base_url + '?start=' + ((page - 1) * per_page);
+		}
+		else
+		{
+			document.location.href = base_url.replace(/&amp;/g, '&') + '&start=' + ((page - 1) * per_page);
+		}
 	}
 }
 
diff --git a/phpBB/styles/subsilver2/template/overall_header.html b/phpBB/styles/subsilver2/template/overall_header.html
index 6db4f85690..a2ed06132d 100644
--- a/phpBB/styles/subsilver2/template/overall_header.html
+++ b/phpBB/styles/subsilver2/template/overall_header.html
@@ -39,12 +39,19 @@ function popup(url, width, height, name)
 function jumpto()
 {
 	var page = prompt('{LA_JUMP_PAGE}:', '{ON_PAGE}');
-	var perpage = '{PER_PAGE}';
+	var per_page = '{PER_PAGE}';
 	var base_url = '{A_BASE_URL}';
 
-	if (page !== null && !isNaN(page) && page > 0)
+	if (page !== null && !isNaN(page) && page == Math.floor(page) && page > 0)
 	{
-		document.location.href = base_url.replace(/&amp;/g, '&') + '&start=' + ((page - 1) * perpage);
+		if (base_url.indexOf('?') == -1)
+		{
+			document.location.href = base_url + '?start=' + ((page - 1) * per_page);
+		}
+		else
+		{
+			document.location.href = base_url.replace(/&amp;/g, '&') + '&start=' + ((page - 1) * per_page);
+		}
 	}
 }