diff --git a/Sources/ZIPFoundation/Archive+ZIP64.swift b/Sources/ZIPFoundation/Archive+ZIP64.swift
index 8b94b7c3..f09a5088 100644
--- a/Sources/ZIPFoundation/Archive+ZIP64.swift
+++ b/Sources/ZIPFoundation/Archive+ZIP64.swift
@@ -80,8 +80,9 @@ extension Archive.ZIP64EndOfCentralDirectoryRecord {
         self.sizeOfZIP64EndOfCentralDirectoryRecord = data.scanValue(start: 4)
         self.versionMadeBy = data.scanValue(start: 12)
         self.versionNeededToExtract = data.scanValue(start: 14)
-        // Version Needed to Extract: 4.5 - File uses ZIP64 format extensions
-        guard self.versionNeededToExtract >= Archive.Version.v45.rawValue else { return nil }
+        // Note: The ZIP spec recommends versionNeededToExtract >= 4.5 for ZIP64,
+        // but some producers (e.g. Microsoft Outlook OLM export) write valid ZIP64
+        // structures with a lower version. We accept the record if the signature matches.
         self.numberOfDisk = data.scanValue(start: 16)
         self.numberOfDiskStart = data.scanValue(start: 20)
         self.totalNumberOfEntriesOnDisk = data.scanValue(start: 24)
diff --git a/Sources/ZIPFoundation/Entry.swift b/Sources/ZIPFoundation/Entry.swift
index a6370c64..e1a31a68 100644
--- a/Sources/ZIPFoundation/Entry.swift
+++ b/Sources/ZIPFoundation/Entry.swift
@@ -297,19 +297,22 @@ extension Entry.CentralDirectoryStructure {
 extension Entry.CentralDirectoryStructure {
 
     var effectiveCompressedSize: UInt64 {
-        if self.isZIP64, let compressedSize = self.zip64ExtendedInformation?.compressedSize, compressedSize > 0 {
+        if self.isZIP64, self.compressedSize == .max,
+           let compressedSize = self.zip64ExtendedInformation?.compressedSize {
             return compressedSize
         }
         return UInt64(compressedSize)
     }
     var effectiveUncompressedSize: UInt64 {
-        if self.isZIP64, let uncompressedSize = self.zip64ExtendedInformation?.uncompressedSize, uncompressedSize > 0 {
+        if self.isZIP64, self.uncompressedSize == .max,
+           let uncompressedSize = self.zip64ExtendedInformation?.uncompressedSize {
             return uncompressedSize
         }
         return UInt64(uncompressedSize)
     }
     var effectiveRelativeOffsetOfLocalHeader: UInt64 {
-        if self.isZIP64, let offset = self.zip64ExtendedInformation?.relativeOffsetOfLocalHeader, offset > 0 {
+        if self.isZIP64, self.relativeOffsetOfLocalHeader == .max,
+           let offset = self.zip64ExtendedInformation?.relativeOffsetOfLocalHeader {
             return offset
         }
         return UInt64(relativeOffsetOfLocalHeader)
diff --git a/Tests/ZIPFoundationTests/ZIPFoundationArchiveTests+ZIP64.swift b/Tests/ZIPFoundationTests/ZIPFoundationArchiveTests+ZIP64.swift
index 95a14dcf..3aec341a 100644
--- a/Tests/ZIPFoundationTests/ZIPFoundationArchiveTests+ZIP64.swift
+++ b/Tests/ZIPFoundationTests/ZIPFoundationArchiveTests+ZIP64.swift
@@ -52,17 +52,19 @@ extension ZIPFoundationTests {
                                                                           additionalDataProvider: {_ -> Data in
                                                                              return Data() })
         XCTAssertNil(invalidEOCDRecord2)
-        let eocdRecordWithWrongVersion: [UInt8] = [0x50, 0x4b, 0x06, 0x06, 0x2c, 0x00, 0x00, 0x00,
-                                                   0x00, 0x00, 0x00, 0x00, 0x1e, 0x03, 0x14, 0x00,
-                                                   0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-                                                   0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-                                                   0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-                                                   0x4c, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
-                                                   0x5a, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]
-        let invalidEOCDRecord3 = Archive.ZIP64EndOfCentralDirectoryRecord(data: Data(eocdRecordWithWrongVersion),
-                                                                          additionalDataProvider: {_ -> Data in
-                                                                             return Data() })
-        XCTAssertNil(invalidEOCDRecord3)
+        // Some ZIP producers (e.g. Microsoft Outlook OLM export) write valid ZIP64
+        // structures with versionNeededToExtract < 4.5. These should be accepted.
+        let eocdRecordWithLowVersion: [UInt8] = [0x50, 0x4b, 0x06, 0x06, 0x2c, 0x00, 0x00, 0x00,
+                                                  0x00, 0x00, 0x00, 0x00, 0x1e, 0x03, 0x14, 0x00,
+                                                  0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                                                  0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                                                  0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                                                  0x4c, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+                                                  0x5a, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00]
+        let lowVersionEOCDRecord = Archive.ZIP64EndOfCentralDirectoryRecord(data: Data(eocdRecordWithLowVersion),
+                                                                            additionalDataProvider: {_ -> Data in
+                                                                               return Data() })
+        XCTAssertNotNil(lowVersionEOCDRecord)
     }
 
     func testArchiveZIP64EOCDLocator() {