diff --git a/app/src/processing/app/SketchController.java b/app/src/processing/app/SketchController.java
index 6f99a1fb6..89f1a3516 100644
--- a/app/src/processing/app/SketchController.java
+++ b/app/src/processing/app/SketchController.java
@@ -846,8 +846,9 @@ public class SketchController {
 
     if (!newName.equals(origName)) {
       String msg =
-        tr("The sketch name had to be modified. Sketch names can only consist\n" +
-          "of ASCII characters and numbers and be less than 64 characters long.");
+        tr("The sketch name had to be modified.\n" +
+          "Sketch names must start with a letter or number, followed by letters,\n" +
+          "numbers, dashes, dots and underscores. Maximum length is 63 characters.");
       System.out.println(msg);
     }
     return newName;
diff --git a/arduino-core/src/cc/arduino/contributions/libraries/LibrariesIndexer.java b/arduino-core/src/cc/arduino/contributions/libraries/LibrariesIndexer.java
index e088cca84..e30ff15f5 100644
--- a/arduino-core/src/cc/arduino/contributions/libraries/LibrariesIndexer.java
+++ b/arduino-core/src/cc/arduino/contributions/libraries/LibrariesIndexer.java
@@ -178,8 +178,8 @@ public class LibrariesIndexer {
           badLibNotified.add(subfolderName);
 
           String mess = I18n.format(tr("The library \"{0}\" cannot be used.\n"
-              + "Library names must contain only basic letters and numbers.\n"
-              + "(ASCII only and no spaces, and it cannot start with a number)"),
+              + "Library folder names must start with a letter or number, followed by letters,\n"
+              + "numbers, dashes, dots and underscores. Maximum length is 63 characters."),
               subfolderName);
           BaseNoGui.showMessage(tr("Ignoring bad library name"), mess);
         }