diff --git a/tests/components/core/test_progmem_string_table.cpp b/tests/components/core/test_progmem_string_table.cpp
index e0d8da56468..72a2c507507 100644
--- a/tests/components/core/test_progmem_string_table.cpp
+++ b/tests/components/core/test_progmem_string_table.cpp
@@ -16,6 +16,29 @@ PROGMEM_STRING_TABLE(LargeStrings, "0123456789012345678901234567890123456789",
                      "5123456789012345678901234567890123456789", "6123456789012345678901234567890123456789",
                      "7123456789012345678901234567890123456789");
 
+// Five 50-character strings pack into exactly 255 bytes; one more byte needs two-byte offsets.
+PROGMEM_STRING_TABLE(Exactly255, "01234567890123456789012345678901234567890123456789",
+                     "01234567890123456789012345678901234567890123456789",
+                     "01234567890123456789012345678901234567890123456789",
+                     "01234567890123456789012345678901234567890123456789",
+                     "01234567890123456789012345678901234567890123456789");
+PROGMEM_STRING_TABLE(Exactly256, "01234567890123456789012345678901234567890123456789",
+                     "01234567890123456789012345678901234567890123456789",
+                     "01234567890123456789012345678901234567890123456789",
+                     "01234567890123456789012345678901234567890123456789",
+                     "01234567890123456789012345678901234567890123456789x");
+
+TEST(ProgmemStringTable, OffsetWidthSwitchesAfter255Bytes) {
+  static_assert(Exactly255::BLOB_SIZE == 255);
+  static_assert(sizeof(Exactly255::OFFSETS[0]) == 1);
+  static_assert(Exactly256::BLOB_SIZE == 256);
+  static_assert(sizeof(Exactly256::OFFSETS[0]) == 2);
+  EXPECT_EQ(Exactly255::OFFSETS[4], 204);
+  EXPECT_EQ(Exactly256::OFFSETS[4], 204);
+  EXPECT_STREQ(reinterpret_cast<const char *>(Exactly256::get_progmem_str(4, 0)),
+               "01234567890123456789012345678901234567890123456789x");
+}
+
 TEST(ProgmemStringTable, SmallTableKeepsOneByteOffsets) {
   static_assert(SmallStrings::BLOB_SIZE <= 255);
   static_assert(sizeof(SmallStrings::OFFSETS[0]) == 1);