diff --git a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/regex/RegexEngineTest.scala b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/regex/RegexEngineTest.scala
index 4cc2a720b4..d174bda341 100644
--- a/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/regex/RegexEngineTest.scala
+++ b/test-suite/shared/src/test/scala/org/scalajs/testsuite/javalib/util/regex/RegexEngineTest.scala
@@ -54,11 +54,12 @@ class RegexEngineTest  {
 
   private def debugEscape(pattern: String): String = {
     pattern.flatMap {
-      case '\t'         => "`t"
-      case '\n'         => "`n"
-      case '\r'         => "`r"
-      case c if c < ' ' => "`x%02X".format(c.toInt)
-      case c            => c.toString()
+      case '\t'          => "`t"
+      case '\n'          => "`n"
+      case '\r'          => "`r"
+      case c if c < 0x10 => "`x0" + c.toInt.toHexString
+      case c if c < ' '  => "`x" + c.toInt.toHexString
+      case c             => c.toString()
     }
   }
 
@@ -1976,8 +1977,52 @@ class RegexEngineTest  {
     val s = compile("s", CaseInsensitive | UnicodeCase)
     assertMatches(s, "s")
     assertMatches(s, "S")
-    assertMatches(s, "\u017F") // ſ LATIN SMALL LETTER LONG S
+    assertMatches(s, "\u017F") // ſ LATIN SMALL LETTER LONG S; 017F folds to 's'
     assertNotMatches(s, "t")
+
+    val ranges = compile("[g-l\uFB00\u0175-\u0182\u0540-\u0550\u1F68-\u1F8E\u1FAA-\u1FAF\u2126]",
+        CaseInsensitive | UnicodeCase)
+    // g-l
+    assertMatches(ranges, "H")
+    assertMatches(ranges, "\u212A") // K KELVIN SIGN, folds to 'k'
+    // FB00
+    assertMatches(ranges, "\uFB00") // ff LATIN SMALL LIGATURE FF
+    // 0175-0182 (contains 017F which folds to 's')
+    if (!executingInJVM) {
+      // https://bugs.openjdk.org/browse/JDK-8360459
+      assertMatches(ranges, "s")
+      assertMatches(ranges, "S")
+    }
+    assertMatches(ranges, "\u017F")
+    assertMatches(ranges, "\u0180") // in range; does not participate in case folding
+    // 0540-0550
+    assertMatches(ranges, "\u0547") // in range
+    assertMatches(ranges, "\u0577") // 0547 folds to 0577
+    // 1F68-1F8E
+    assertMatches(ranges, "\u1F65") // 1F6D folds to 1F65
+    assertMatches(ranges, "\u1F6D") // in range
+    assertMatches(ranges, "\u1F82") // 1F8A folds to 1F82, and 1F82 is also in range
+    // 1FAA-1FAF
+    assertMatches(ranges, "\u1FA4") // 1FAC folds to 1FA4 only in simple case folding
+    // 2126
+    assertMatches(ranges, "\u2126") // in the set
+    assertMatches(ranges, "\u03C9") // 2126 folds to 03C9
+    assertMatches(ranges, "\u03A9") // 03A9 also folds to 03C9
+    // No matches
+    assertNotMatches(ranges, "t")
+    assertNotMatches(ranges, "ff") // ff FB00 would only match with full case folding
+
+    // Demonstrate that the JVM recognizes 017F as folding to 's' if the range is ASCII
+    val rangeWithASCII_S = compile("[P-U]", CaseInsensitive | UnicodeCase)
+    assertMatches(rangeWithASCII_S, "s")
+    assertMatches(rangeWithASCII_S, "S")
+    assertMatches(rangeWithASCII_S, "\u017F")
+
+    // Demonstrate that the JVM recognizes 017F as folding to 's' if it is not a range
+    val nonRangeWith_017F = compile("[\u017F\u0184]", CaseInsensitive | UnicodeCase)
+    assertMatches(nonRangeWith_017F, "s")
+    assertMatches(nonRangeWith_017F, "S")
+    assertMatches(nonRangeWith_017F, "\u017F")
   }
 
   @Test def wordBoundary(): Unit = {