diff --git a/src/etapi/validators.js b/src/etapi/validators.js
index 7b3ba852c..f02d6a4ab 100644
--- a/src/etapi/validators.js
+++ b/src/etapi/validators.js
@@ -16,7 +16,7 @@ function isString(obj) {
     if (obj === undefined || obj === null) {
         return;
     }
-    
+
     if (typeof obj !== 'string') {
         return `'${obj}' is not a string`;
     }
@@ -26,7 +26,7 @@ function isBoolean(obj) {
     if (obj === undefined || obj === null) {
         return;
     }
-    
+
     if (typeof obj !== 'boolean') {
         return `'${obj}' is not a boolean`;
     }
@@ -36,7 +36,7 @@ function isInteger(obj) {
     if (obj === undefined || obj === null) {
         return;
     }
-    
+
     if (!Number.isInteger(obj)) {
         return `'${obj}' is not an integer`;
     }
@@ -46,13 +46,13 @@ function isNoteId(obj) {
     if (obj === undefined || obj === null) {
         return;
     }
-    
+
     const becca = require('../becca/becca');
-    
+
     if (typeof obj !== 'string') {
         return `'${obj}' is not a valid noteId`;
     }
-    
+
     if (!(obj in becca.notes)) {
         return `Note '${obj}' does not exist`;
     }
@@ -84,8 +84,8 @@ function isValidEntityId(obj) {
     if (obj === undefined || obj === null) {
         return;
     }
-    
-    if (typeof obj !== 'string' || !/^[A-Za-z0-9]{4,32}$/.test(obj)) {
+
+    if (typeof obj !== 'string' || !/^[A-Za-z0-9_]{4,128}$/.test(obj)) {
         return `'${obj}' is not a valid entityId. Only alphanumeric characters are allowed of length 4 to 32.`;
     }
 }
@@ -100,4 +100,4 @@ module.exports = {
     isNoteType,
     isAttributeType,
     isValidEntityId
-};
\ No newline at end of file
+};
diff --git a/src/services/export/zip.js b/src/services/export/zip.js
index 9b73d1b8c..3fdaa2dd5 100644
--- a/src/services/export/zip.js
+++ b/src/services/export/zip.js
@@ -214,13 +214,13 @@ function exportToZip(taskContext, branch, format, res) {
     }
 
     function findLinks(content, noteMeta) {
-        content = content.replace(/src="[^"]*api\/images\/([a-zA-Z0-9]+)\/[^"]*"/g, (match, targetNoteId) => {
+        content = content.replace(/src="[^"]*api\/images\/([a-zA-Z0-9_]+)\/[^"]*"/g, (match, targetNoteId) => {
             const url = getTargetUrl(targetNoteId, noteMeta);
 
             return url ? `src="${url}"` : match;
         });
 
-        content = content.replace(/href="[^"]*#root[a-zA-Z0-9\/]*\/([a-zA-Z0-9]+)\/?"/g, (match, targetNoteId) => {
+        content = content.replace(/href="[^"]*#root[a-zA-Z0-9_\/]*\/([a-zA-Z0-9_]+)\/?"/g, (match, targetNoteId) => {
             const url = getTargetUrl(targetNoteId, noteMeta);
 
             return url ? `href="${url}"` : match;
diff --git a/src/services/import/enex.js b/src/services/import/enex.js
index dde601a72..b00d2e21b 100644
--- a/src/services/import/enex.js
+++ b/src/services/import/enex.js
@@ -115,7 +115,7 @@ function importEnex(taskContext, file, parentNote) {
             let labelName = currentTag;
 
             if (labelName === 'source-url') {
-                labelName = 'sourceUrl';
+                labelName = 'pageUrl';
             }
 
             labelName = sanitizeAttributeName(labelName);
@@ -139,7 +139,7 @@ function importEnex(taskContext, file, parentNote) {
             else if (currentTag === 'source-url') {
                 resource.attributes.push({
                     type: 'label',
-                    name: 'sourceUrl',
+                    name: 'pageUrl',
                     value: text
                 });
             }
diff --git a/src/services/import/zip.js b/src/services/import/zip.js
index d1997f31f..262ef4691 100644
--- a/src/services/import/zip.js
+++ b/src/services/import/zip.js
@@ -230,6 +230,13 @@ async function importZip(taskContext, fileBuffer, importRootNote) {
         absUrl += `${absUrl.length > 0 ? '/' : ''}${url}`;
 
         const {noteMeta} = getMeta(absUrl);
+
+        if (!noteMeta) {
+            log.info(`Could not find note meta for URL '${absUrl}'.`);
+
+            return null;
+        }
+
         const targetNoteId = getNoteId(noteMeta, absUrl);
         return targetNoteId;
     }
@@ -266,6 +273,10 @@ async function importZip(taskContext, fileBuffer, importRootNote) {
 
             const targetNoteId = getNoteIdFromRelativeUrl(url, filePath);
 
+            if (!targetNoteId) {
+                return match;
+            }
+
             return `src="api/images/${targetNoteId}/${path.basename(url)}"`;
         });
 
@@ -284,6 +295,10 @@ async function importZip(taskContext, fileBuffer, importRootNote) {
 
             const targetNoteId = getNoteIdFromRelativeUrl(url, filePath);
 
+            if (!targetNoteId) {
+                return match;
+            }
+
             return `href="#root/${targetNoteId}"`;
         });