diff --git a/cache/js/.empty b/cache/js/.empty
new file mode 100644
index 000000000..e69de29bb
diff --git a/include/functions.php b/include/functions.php
index b43fda3a1..8c2ced801 100644
--- a/include/functions.php
+++ b/include/functions.php
@@ -3907,4 +3907,32 @@
 		return in_array($interface, class_implements($class));
 	}
 
+	function get_minified_js($files) {
+		require_once 'lib/jshrink/Minifier.php';
+
+		$rv = '';
+
+		foreach ($files as $js) {
+			if (!isset($_GET['debug'])) {
+				$cached_file = CACHE_DIR . "/js/$js.js";
+
+				if (file_exists($cached_file) &&
+						is_readable($cached_file) &&
+						filemtime($cached_file) >= filemtime("js/$js.js")) {
+
+					$rv .= file_get_contents($cached_file);
+
+				} else {
+					$minified = JShrink\Minifier::minify(file_get_contents("js/$js.js"));
+					file_put_contents($cached_file, $minified);
+					$rv .= $minified;
+				}
+			} else {
+				$rv .= file_get_contents("js/$js.js");
+			}
+		}
+
+		return $rv;
+	}
+
 ?>
diff --git a/include/sanity_check.php b/include/sanity_check.php
index fcf548705..4925486a3 100644
--- a/include/sanity_check.php
+++ b/include/sanity_check.php
@@ -36,6 +36,10 @@
 				array_push($errors, "Data export cache is not writable (chmod -R 777 ".CACHE_DIR."/export)");
 			}
 
+			if (!is_writable(CACHE_DIR . "/js")) {
+				array_push($errors, "Javascript cache is not writable (chmod -R 777 ".CACHE_DIR."/js)");
+			}
+
 			if (GENERATED_CONFIG_CHECK != EXPECTED_CONFIG_VERSION) {
 				array_push($errors,
 					"Configuration option checker sanity_config.php is outdated, please recreate it using ./utils/regen_config_checks.sh");
diff --git a/index.php b/index.php
index 49fcfdf98..68d6fc753 100644
--- a/index.php
+++ b/index.php
@@ -95,13 +95,9 @@
 			}
 		}
 
-		foreach (array("tt-rss", "functions", "feedlist", "viewfeed", "FeedTree") as $js) {
-			if (!isset($_GET['debug'])) {
-				echo JShrink\Minifier::minify(file_get_contents("js/$js.js"));
-			} else {
-				echo file_get_contents("js/$js.js");
-			}
-		}
+		print get_minified_js(array("tt-rss",
+			"functions", "feedlist", "viewfeed", "FeedTree"));
+
 	?>
 	</script>
 
diff --git a/prefs.php b/prefs.php
index 4027fd1fa..a47d00bce 100644
--- a/prefs.php
+++ b/prefs.php
@@ -54,13 +54,8 @@
 			}
 		}
 
-		foreach (array("functions", "deprecated", "prefs") as $js) {
-			if (!isset($_GET['debug'])) {
-				echo JShrink\Minifier::minify(file_get_contents("js/$js.js"));
-			} else {
-				echo file_get_contents("js/$js.js");
-			}
-		}
+		print get_minified_js(array("functions", "deprecated", "prefs"));
+
 	?>
 	</script>