diff --git a/_locales/en/messages.json b/_locales/en/messages.json
index 64e407be..90890e7e 100644
--- a/_locales/en/messages.json
+++ b/_locales/en/messages.json
@@ -157,6 +157,10 @@
 		"message": "Remove section",
 		"description": "Label for the button to remove a section"
 	},
+	"styleBadRegexp": {
+		"message": "Regexp is invalid.",
+		"description": "Validation message for a bad regexp in a style"
+	},
 	"styleCancelEditLabel": {
 		"message": "Back to manage",
 		"description": "Label for cancel button for style editing"
@@ -223,4 +227,4 @@
 		"message": "Update completed.",
 		"description": "Text that displays when an update completed"
 	}
-}
\ No newline at end of file
+}
diff --git a/background.js b/background.js
index 1c257e73..84ac06bd 100644
--- a/background.js
+++ b/background.js
@@ -159,7 +159,13 @@ function sectionAppliesToUrl(section, url) {
 		if (regexp[regexp.length - 1] != "$") {
 			regexp += "$";
 		}
-		return (new RegExp(regexp)).test(url);
+		try {
+			var re = new RegExp(regexp);
+		} catch (ex) {
+			console.log(section.id + "'s regexp '" + regexp + "' is not valid");
+			return false;
+		}
+		return (re).test(url);
 	})) {
 		console.log(section.id + " applies to " + url + " due to regexp rules");
 		return true;
diff --git a/edit.js b/edit.js
index a1fc8857..44f4b032 100644
--- a/edit.js
+++ b/edit.js
@@ -149,6 +149,30 @@ function validate() {
 	if (name == "") {
 		return t("styleMissingName");
 	}
+	// validate the regexps
+	if (Array.prototype.some.call(document.querySelectorAll(".applies-to-list"), function(list) {
+		return Array.prototype.some.call(list.childNodes, function(li) {
+			if (li.className == appliesToEverythingTemplate.className) {
+				return false;
+			}
+			var valueElement = li.querySelector("[name=applies-value]");
+			var a = li.querySelector("[name=applies-type]").value;
+			var b = valueElement.value;
+			if (a && b) {
+				if (a == "regexp") {
+					try {
+						new RegExp(b);
+					} catch (ex) {
+						valueElement.focus();
+						return true;
+					}
+				}
+			}
+			return false;
+		});
+	})) {
+		return t("styleBadRegexp");
+	}
 	return null;
 }