diff --git a/src/Errors.h b/src/Errors.h
index 20915280f..8b35bfd6e 100644
--- a/src/Errors.h
+++ b/src/Errors.h
@@ -109,6 +109,7 @@ enum CC_ERRORS {
 	INF_ERR_NUM_CODES    = 0xCCDED056UL, /* Too many codewords specified for bit length */
 
 	ERR_DOWNLOAD_INVALID = 0xCCDED057UL, /* Unspecified error occurred downloading data */
-	ERR_NO_AUDIO_OUTPUT  = 0xCCDED058UL  /* No audio output devices are connected */
+	ERR_NO_AUDIO_OUTPUT  = 0xCCDED058UL, /* No audio output devices are connected */
+	ERR_INVALID_URL      = 0xCCDED059UL  /* Invalid URL provided to download from */
 };
 #endif
diff --git a/src/Http_Web.c b/src/Http_Web.c
index ec78856b7..c652306ef 100644
--- a/src/Http_Web.c
+++ b/src/Http_Web.c
@@ -3,7 +3,7 @@
 #include "_HttpBase.h"
 #include <emscripten/emscripten.h>
 #include "Errors.h"
-extern void interop_DownloadAsync(const char* url, int method, int reqID);
+extern int interop_DownloadAsync(const char* url, int method, int reqID);
 extern int interop_IsHttpsOnly(void);
 static struct RequestList workingReqs, queuedReqs;
 
@@ -54,6 +54,7 @@ static void Http_StartNextDownload(void) {
 	char urlBuffer[URL_MAX_SIZE]; cc_string url;
 	char urlStr[NATIVE_STR_LEN];
 	struct HttpRequest* req;
+	cc_result res;
 
 	/* Avoid making too many requests at once */
 	if (workingReqs.count >= HTTP_MAX_CONCURRENCY) return;
@@ -65,9 +66,21 @@ static void Http_StartNextDownload(void) {
 	Platform_Log1("Fetching %s", &url);
 
 	Platform_EncodeUtf8(urlStr, &url);
-	interop_DownloadAsync(urlStr, req->requestType, req->id);
-	RequestList_Append(&workingReqs, req, false);
-	RequestList_RemoveAt(&queuedReqs, 0);
+	res = interop_DownloadAsync(urlStr, req->requestType, req->id);
+	
+	if (res) {
+		/* Download error code -> ClassiCube error code */
+		if (res == 1) res = ERR_INVALID_URL;
+		req->result = res;
+		
+		/* Invalid URL so move onto next request */
+		Http_FinishRequest(req);
+		RequestList_RemoveAt(&queuedReqs, 0);
+		Http_StartNextDownload();
+	} else {
+		RequestList_Append(&workingReqs, req, false);
+		RequestList_RemoveAt(&queuedReqs, 0);
+	}
 }
 
 EMSCRIPTEN_KEEPALIVE void Http_OnUpdateProgress(int reqID, int read, int total) {
diff --git a/src/Logger.c b/src/Logger.c
index 21caaabd6..06c4aa96b 100644
--- a/src/Logger.c
+++ b/src/Logger.c
@@ -81,7 +81,8 @@ static const char* GetCCErrorDesc(cc_result res) {
 	case CW_ERR_STRING_LEN: return "NBT string too long";
 
 	case ERR_DOWNLOAD_INVALID: return "Website denied download or doesn't exist";
-	case ERR_NO_AUDIO_OUTPUT: return "No audio output devices plugged in";
+	case ERR_NO_AUDIO_OUTPUT:  return "No audio output devices plugged in";
+	case ERR_INVALID_URL:      return "Cannot download from invalid URL";
 	}
 	return NULL;
 }
diff --git a/src/interop_web.js b/src/interop_web.js
index f06116975..877e6f133 100644
--- a/src/interop_web.js
+++ b/src/interop_web.js
@@ -50,7 +50,15 @@ mergeInto(LibraryManager.library, {
     var onProgress = Module["_Http_OnUpdateProgress"];
 
     var xhr = new XMLHttpRequest();
-    xhr.open(reqMethod, url);
+    try {
+      xhr.open(reqMethod, url);
+    } catch (e) {
+      // DOMException gets thrown when invalid URL provided. Test cases:
+      //   http://%7https://www.example.com/test.zip
+      //   http://example:app/test.zip
+      console.log(e);
+      return 1;
+    }  
     xhr.responseType = 'arraybuffer';
 
     var getContentLength = function(e) {
@@ -74,6 +82,7 @@ mergeInto(LibraryManager.library, {
     xhr.onprogress = function(e) { onProgress(reqID, e.loaded, e.total); };
 
     try { xhr.send(); } catch (e) { onFinished(reqID, 0, 0, 0); }
+    return 0;
   },
   interop_IsHttpsOnly : function() {
     // If this webpage is https://, browsers deny any http:// downloading