diff --git a/PasZip.pas b/PasZip.pas
index d80fc9a6a..29a272a9f 100644
--- a/PasZip.pas
+++ b/PasZip.pas
@@ -36,6 +36,10 @@
    - .zip reading from file, resource or direct memory - Windows only
    - .zip write into a file (new .zip creation, not update) - Windows only
 
+   This unit is a cut-down stand-alone zip reader/writer, to be used e.g.
+   in installers or size-critical projects. Consider mormot.core.zip.pas from
+   mORMot 2 for more features, and better performance (thanks to libdeflate).
+
 }
 
 {$WARNINGS OFF}
@@ -334,6 +338,7 @@ implementation
 {$ifndef FPC}
 type
   PtrUInt = {$ifdef CPU64}NativeUInt{$else}cardinal{$endif};
+  PtrInt  = {$ifdef CPU64}NativeInt {$else}integer {$endif};
 {$endif FPC}
 
 // special tuned Move() routine, including data overlap bug correction
@@ -3810,9 +3815,13 @@ procedure CreateVoidZip(const aFileName: TFileName);
   FileClose(H);
 end;
 
-
 {$ifdef MSWINDOWS}
 
+function ValidHandle(Handle: THandle): boolean; {$ifdef HASINLINE}inline;{$endif}
+begin
+  result := PtrInt(Handle) > 0;
+end;
+
 type
   splitInt64 = packed record
     loCard, hiCard: cardinal
@@ -3831,10 +3840,10 @@ function CompressFile(const srcFile, dstFile: TFileName; failIfGrow: boolean): b
   try
     sf := CreateFile(pointer(srcFile), GENERIC_READ, FILE_SHARE_READ or
       FILE_SHARE_WRITE, nil, OPEN_EXISTING, 0, 0);
-    if sf <> INVALID_HANDLE_VALUE then begin
+    if ValidHandle(sf) then begin
       df := CreateFile(pointer(dstFile), GENERIC_READ or GENERIC_WRITE, 0, nil,
         CREATE_ALWAYS, 0, 0);
-      if df <> INVALID_HANDLE_VALUE then begin
+      if ValidHandle(df) then begin
         sm := CreateFileMapping(sf, nil, PAGE_READONLY, 0, 0, nil);
         if sm <> 0 then begin
           splitInt64(sl).loCard := GetFileSize(sf, @splitInt64(sl).hiCard);
@@ -3907,10 +3916,10 @@ function UncompressFile(const srcFile, dstFile: TFileName; lastWriteTime: int64;
     sf := CreateFile(pointer(srcFile), GENERIC_READ, FILE_SHARE_READ or
       FILE_SHARE_WRITE, nil, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL or
       FILE_FLAG_SEQUENTIAL_SCAN, 0);
-    if sf <> INVALID_HANDLE_VALUE then begin
+    if ValidHandle(sf) then begin
       df := CreateFile(pointer(dstFile), GENERIC_READ or GENERIC_WRITE, 0, nil,
         CREATE_ALWAYS, attr or FILE_FLAG_SEQUENTIAL_SCAN, 0);
-      if df <> INVALID_HANDLE_VALUE then begin
+      if ValidHandle(df) then begin
         sm := CreateFileMapping(sf, nil, PAGE_READONLY, 0, 0, nil);
         if sm <> 0 then begin
           sb := MapViewOfFile(sm, FILE_MAP_READ, 0, 0, 0);
@@ -3991,7 +4000,7 @@ function GetCompressedFileInfo(const comprFile: TFileName; var size: int64;
   crc32 := 0;
   file_ := CreateFile(pointer(comprFile), GENERIC_READ, FILE_SHARE_READ or
     FILE_SHARE_WRITE, nil, OPEN_EXISTING, 0, 0);
-  if file_ <> INVALID_HANDLE_VALUE then begin
+  if ValidHandle(file_) then begin
     result := ReadFile(file_, size, 8, c1, nil) and (c1 = 8) and ReadFile(file_,
       crc32, 4, c1, nil) and (c1 = 4);
     CloseHandle(file_);
@@ -4007,7 +4016,7 @@ function GetUncompressedFileInfo(const uncomprFile: TFileName; var size: int64;
   result := false;
   file_ := CreateFile(pointer(uncomprFile), GENERIC_READ, FILE_SHARE_READ or
     FILE_SHARE_WRITE, nil, OPEN_EXISTING, 0, 0);
-  if file_ <> INVALID_HANDLE_VALUE then begin
+  if ValidHandle(file_) then begin
     splitInt64(size).loCard := GetFileSize(file_, @splitInt64(size).hiCard);
     map := CreateFileMapping(file_, nil, PAGE_READONLY, 0, 0, nil);
     if map <> 0 then begin
@@ -4069,14 +4078,11 @@ function Zip(const zip: TFileName; const files, zipAs: array of TFileName;
   NoSubDirectories: boolean = false): boolean;
 var
   i1, i2, i3: integer;
-  dstFh: THandle;
-  srcFh: THandle;
+  dstFh, srcFh: THandle;
   ft: TFileTime;
-  c1: dword;
+  c1, size: dword;
   lfhr: TLocalFileHeader;
-  srcBuf: pointer;
-  dstBuf: pointer;
-  size: dword;
+  srcBuf, dstBuf: pointer;
   zipRec: array of record
     name: TZipName;
     fhr: TFileHeader;
@@ -4084,7 +4090,7 @@ function Zip(const zip: TFileName; const files, zipAs: array of TFileName;
   lhr: TLastHeader;
 begin
   dstFh := CreateFile(pointer(zip), GENERIC_WRITE, 0, nil, CREATE_ALWAYS, 0, 0);
-  result := dstFh <> INVALID_HANDLE_VALUE;
+  result := ValidHandle(dstFh);
   if result then begin
     SetLength(zipRec, Length(files));
     i2 := 0;
@@ -4103,7 +4109,7 @@ function Zip(const zip: TFileName; const files, zipAs: array of TFileName;
           name := TZipName(zipAs[i1]);
         srcFh := CreateFile(pointer(files[i1]), GENERIC_READ, FILE_SHARE_READ,
           nil, OPEN_EXISTING, 0, 0);
-        if srcFh <> INVALID_HANDLE_VALUE then begin
+        if ValidHandle(srcFh) then begin
           size := GetFileSize(srcFh, nil);
           srcBuf := pointer(LocalAlloc(LPTR, size));
           if srcBuf <> nil then begin
@@ -4230,6 +4236,7 @@ procedure InitCrc32Tab;
 end;
 {$endif}
 
+
 {$ifdef MSWINDOWS}
 
 { TZipRead }
@@ -4314,7 +4321,7 @@ constructor TZipRead.Create(const aFileName: TFileName; ZipStartOffset, Size:
   fShowMessageBoxOnError := ShowMessageBoxOnError;
   file_ := CreateFile(pointer(aFileName), GENERIC_READ, FILE_SHARE_READ, nil,
     OPEN_EXISTING, 0, 0);
-  if file_ = INVALID_HANDLE_VALUE then
+  if not ValidHandle(file_) then
     exit; // file doesn't exist -> leave no Entry[] (Count=0)
   if Size = 0 then
     Size := GetFileSize(file_, nil);
@@ -4345,13 +4352,13 @@ constructor TZipRead.Create(const aFileName: TFileName; ZipStartOffset, Size:
 procedure TZipRead.UnMap;
 begin
   Count := 0;
-  if file_ <> INVALID_HANDLE_VALUE then begin
+  if ValidHandle(file_) then begin
     if map <> 0 then begin
       UnmapViewOfFile(Buf);
       CloseHandle(map);
     end;
     CloseHandle(file_);
-    file_ := INVALID_HANDLE_VALUE;
+    file_ := 0;
   end;
   Buf := nil;
 end;
@@ -4453,7 +4460,7 @@ function TZipRead.CheckFile(aIndex: integer; DestPath: TFileName): boolean;
     DestPath := DestPath + '\';
   F := CreateFile(pointer(DestPath + Entry[aIndex].Name), GENERIC_READ,
     FILE_SHARE_READ, nil, OPEN_EXISTING, 0, 0);
-  if F <> INVALID_HANDLE_VALUE then
+  if ValidHandle(F) then
     with Entry[aIndex] do
     try
       Size := GetFileSize(F, nil);
@@ -4508,7 +4515,7 @@ function TZipRead.UnZipFile(aIndex: integer; DestPath: TFileName;
 {$endif}
     f := DestPath + n;
     H := FileOpen(f, fmOpenRead);
-    if H <> INVALID_HANDLE_VALUE then begin
+    if ValidHandle(H) then begin
       GetFileTime(H, nil, nil, @fFileTime);
       FileTimeToLocalFileTime(fFileTime, fFileTime);
       fFileSize := GetFileSize(H, nil);
@@ -4524,7 +4531,7 @@ function TZipRead.UnZipFile(aIndex: integer; DestPath: TFileName;
     end;
     ForceDirectories(ExtractFileDir(f));
     H := FileCreate(f);
-    if H <> INVALID_HANDLE_VALUE then
+    if ValidHandle(H) then
     try
       if info^.zZipMethod = 0 then begin // stored method
         if info^.zcrc32 <> not UpdateCrc32(dword(-1), data, info^.zfullSize) then
@@ -4612,26 +4619,31 @@ procedure TZipWrite.AddDeflated(const aFileName: TFileName; RemovePath: boolean;
   FileTime: LongRec;
 begin
   H := FileOpen(aFileName, fmOpenRead or fmShareDenyNone);
-  if H = INVALID_HANDLE_VALUE then
-    exit;
-  if RemovePath then
-    ZipName := TZipName(ExtractFileName(aFileName))
-  else
-    ZipName := TZipName(aFileName);
-  GetFileTime(H, nil, nil, @Time);
-  FileTimeToLocalFileTime(Time, Time);
-  FileTimeToDosDateTime(Time, FileTime.Hi, FileTime.Lo);
-  Size := GetFileSize(H, nil);
-  getmem(buf, Size);
-  FileRead(H, buf^, Size);
-  AddDeflated(ZipName, buf, size, CompressLevel, integer(FileTime));
-  freemem(buf);
-  FileClose(H);
+  if ValidHandle(H) then
+  try
+    if RemovePath then
+      ZipName := TZipName(ExtractFileName(aFileName))
+    else
+      ZipName := TZipName(aFileName);
+    GetFileTime(H, nil, nil, @Time);
+    FileTimeToLocalFileTime(Time, Time);
+    FileTimeToDosDateTime(Time, FileTime.Hi, FileTime.Lo);
+    Size := GetFileSize(H, nil);
+    getmem(buf, Size);
+    try
+      FileRead(H, buf^, Size);
+      AddDeflated(ZipName, buf, size, CompressLevel, integer(FileTime));
+    finally
+      freemem(buf);
+    end;
+  finally
+    FileClose(H);
+  end;
 end;
 
 procedure TZipWrite.AddFromZip(const ZipEntry: TZipEntry);
 begin
-  if (self = nil) or (Handle = 0) or (Handle = integer(INVALID_HANDLE_VALUE)) then
+  if (self = nil) or not ValidHandle(Handle) then
     exit;
   if Count >= length(Entry) then
     SetLength(Entry, length(Entry) + 20);
@@ -4656,7 +4668,7 @@ procedure TZipWrite.AddFromZip(const ZipEntry: TZipEntry);
 procedure TZipWrite.AddStored(const aZipName: TZipName; Buf: pointer; Size,
   FileAge: integer);
 begin
-  if (self = nil) or (Handle = 0) or (Handle = integer(INVALID_HANDLE_VALUE)) then
+  if (self = nil) or not ValidHandle(Handle) then
     exit;
   if Count >= length(Entry) then
     SetLength(Entry, length(Entry) + 20);
@@ -4684,7 +4696,7 @@ procedure TZipWrite.AddStored(const aZipName: TZipName; Buf: pointer; Size,
 
 procedure TZipWrite.Append(const Content: RawByteZip);
 begin
-  if (self = nil) or (Handle = 0) or (Handle = integer(INVALID_HANDLE_VALUE)) or
+  if (self = nil) or not ValidHandle(Handle) or
     (fAppendOffset <> 0) then
     exit;
   fAppendOffset := length(Content);
diff --git a/SynopseCommit.inc b/SynopseCommit.inc
index ec9055f7d..eeadcb539 100644
--- a/SynopseCommit.inc
+++ b/SynopseCommit.inc
@@ -1 +1 @@
-'1.18.7657'
+'1.18.7658'