diff --git a/content/addon.js b/content/addon.js
index f614fb0..514437f 100644
--- a/content/addon.js
+++ b/content/addon.js
@@ -92,12 +92,10 @@ let Addon = {
 		let appver;
 		if (Services.appinfo.name == "Pale Moon") {
 			appver = "27.9";
-		} else if (Services.appinfo.name == "SeaMonkey") {
-			appver = "52.0";
-		} else {
+		} else if (Services.appinfo.name != "SeaMonkey") {
 			appver = Services.appinfo.version;
 		}
-		if (Services.vc.compare(dbQuery.row.min, appver) <= 0 && Services.vc.compare(appver, dbQuery.row.max) <= 0) {
+		if (appver && Services.vc.compare(dbQuery.row.min, appver) <= 0 && Services.vc.compare(appver, dbQuery.row.max) <= 0) {
 			data.compat = "add";
 			data.action = "Install Now";
 			data.downurl = "https://addons.mozilla.org/firefox/downloads/file/" + dbQuery.row.url;
diff --git a/content/list.js b/content/list.js
index 5cd8055..5ba91a0 100644
--- a/content/list.js
+++ b/content/list.js
@@ -172,12 +172,10 @@ let List = {
 			let appver;
 			if (Services.appinfo.name == "Pale Moon") {
 				appver = "27.9";
-			} else if (Services.appinfo.name == "SeaMonkey") {
-				appver = "52.0";
-			} else {
+			} else if (Services.appinfo.name != "SeaMonkey") {
 				appver = Services.appinfo.version;
 			}
-			if (Services.vc.compare(dbQuery.row.min, appver) <= 0 && Services.vc.compare(appver, dbQuery.row.max) <= 0) {
+			if (appver && Services.vc.compare(dbQuery.row.min, appver) <= 0 && Services.vc.compare(appver, dbQuery.row.max) <= 0) {
 				item = item.replace("%COMPAT%", "add");
 				item = item.replace("%ACTION%", "Install Now");
 				item = item.replace("%DOWNURL%", "https://addons.mozilla.org/firefox/downloads/file/" + dbQuery.row.url);
diff --git a/content/versions.js b/content/versions.js
index 53e679c..9b0ac10 100644
--- a/content/versions.js
+++ b/content/versions.js
@@ -110,12 +110,10 @@ let Versions = {
 			let appver;
 			if (Services.appinfo.name == "Pale Moon") {
 				appver = "27.9";
-			} else if (Services.appinfo.name == "SeaMonkey") {
-				appver = "52.0";
-			} else {
+			} else if (Services.appinfo.name != "SeaMonkey") {
 				appver = Services.appinfo.version;
 			}
-			if (Services.vc.compare(dbQuery.row.min, appver) <= 0 && Services.vc.compare(appver, dbQuery.row.max) <= 0) {
+			if (appver && Services.vc.compare(dbQuery.row.min, appver) <= 0 && Services.vc.compare(appver, dbQuery.row.max) <= 0) {
 				item = item.replace("%COMPAT%", "add");
 				item = item.replace("%ACTION%", "Install Now");
 				item = item.replace("%DOWNURL%", "https://addons.mozilla.org/firefox/downloads/file/" + dbQuery.row.url);