diff --git a/icu4c/source/test/intltest/numbertest_stringsegment.cpp b/icu4c/source/test/intltest/numbertest_stringsegment.cpp
index 34c4356c7d0..bb54781cb97 100644
--- a/icu4c/source/test/intltest/numbertest_stringsegment.cpp
+++ b/icu4c/source/test/intltest/numbertest_stringsegment.cpp
@@ -77,18 +77,15 @@ void StringSegmentTest::testCommonPrefixLength() {
     assertEquals("", 4, segment.getCommonPrefixLength(u"📻 r"));
     assertEquals("", 3, segment.getCommonPrefixLength(u"📻 x"));
     assertEquals("", 0, segment.getCommonPrefixLength(u"x"));
-    assertEquals("", 0, segment.getCommonPrefixLength(u""));
     segment.adjustOffset(3);
     assertEquals("", 0, segment.getCommonPrefixLength(u"RADiO"));
     assertEquals("", 5, segment.getCommonPrefixLength(u"radio"));
     assertEquals("", 2, segment.getCommonPrefixLength(u"rafio"));
     assertEquals("", 0, segment.getCommonPrefixLength(u"fadio"));
-    assertEquals("", 0, segment.getCommonPrefixLength(u""));
     segment.setLength(3);
     assertEquals("", 3, segment.getCommonPrefixLength(u"radio"));
     assertEquals("", 2, segment.getCommonPrefixLength(u"rafio"));
     assertEquals("", 0, segment.getCommonPrefixLength(u"fadio"));
-    assertEquals("", 0, segment.getCommonPrefixLength(u""));
     segment.resetLength();
     segment.setOffset(11); // end of string
     assertEquals("", 0, segment.getCommonPrefixLength(u"foo"));
diff --git a/icu4j/main/tests/core/src/com/ibm/icu/dev/test/impl/StringSegmentTest.java b/icu4j/main/tests/core/src/com/ibm/icu/dev/test/impl/StringSegmentTest.java
index 3434f6454a3..179e0935a08 100644
--- a/icu4j/main/tests/core/src/com/ibm/icu/dev/test/impl/StringSegmentTest.java
+++ b/icu4j/main/tests/core/src/com/ibm/icu/dev/test/impl/StringSegmentTest.java
@@ -73,20 +73,17 @@ public class StringSegmentTest {
         assertEquals(4, segment.getCommonPrefixLength("📻 r"));
         assertEquals(3, segment.getCommonPrefixLength("📻 x"));
         assertEquals(0, segment.getCommonPrefixLength("x"));
-        assertEquals(0, segment.getCommonPrefixLength(""));
         segment.adjustOffset(3);
         assertEquals(5, segment.getCommonPrefixLength("raDio"));
         assertEquals(5, segment.getCommonPrefixLength("radio"));
         assertEquals(2, segment.getCommonPrefixLength("rafio"));
         assertEquals(0, segment.getCommonPrefixLength("fadio"));
-        assertEquals(0, segment.getCommonPrefixLength(""));
         assertEquals(5, segment.getCaseSensitivePrefixLength("radio"));
         assertEquals(2, segment.getCaseSensitivePrefixLength("raDio"));
         segment.setLength(3);
         assertEquals(3, segment.getCommonPrefixLength("radio"));
         assertEquals(2, segment.getCommonPrefixLength("rafio"));
         assertEquals(0, segment.getCommonPrefixLength("fadio"));
-        assertEquals(0, segment.getCommonPrefixLength(""));
         segment.resetLength();
         segment.setOffset(11); // end of string
         assertEquals(0, segment.getCommonPrefixLength("foo"));