diff --git a/components/lazutils/lazutf8.pas b/components/lazutils/lazutf8.pas
index 864570f472..44820b857c 100644
--- a/components/lazutils/lazutf8.pas
+++ b/components/lazutils/lazutf8.pas
@@ -84,8 +84,8 @@ function UTF8Length(p: PChar; ByteCount: PtrInt): PtrInt;
 function UTF8LengthFast(const s: string): PtrInt; inline;
 function UTF8LengthFast(p: PChar; ByteCount: PtrInt): PtrInt;
 
-function UTF8CodepointCount(const s: string): PtrInt; inline;
-function UTF8CodepointCount(p: PChar; ByteCount: PtrInt): PtrInt;
+function UTF8CodepointCount(const s: string): SizeInt; inline;
+function UTF8CodepointCount(p: PChar; ByteCount: SizeInt): SizeInt;
 
 // Functions dealing with unicode number U+xxx.
 function UTF8CodepointToUnicode(p: PChar; out CodepointLen: integer): Cardinal;
@@ -575,16 +575,18 @@ begin
   Result:=UTF8CodepointCount(PChar(s),length(s));
 end;
 
-function UTF8CodepointCount(p: PChar; ByteCount: PtrInt): PtrInt;
+function UTF8CodepointCount(p: PChar; ByteCount: SizeInt): SizeInt;
 var
-  codepointLen: LongInt;
+  codepointLen: SizeInt;
 begin
   Result:=0;
   while (ByteCount>0) do begin
-    inc(Result);
-    codepointLen:=UTF8CodepointLen(p,ByteCount,false);
-    if codepointLen=0 then
+    codepointLen:=UTF8CodepointLen(p,ByteCount,False);
+    if codepointLen >= 0 then
+      inc(Result);
+    if codepointLen = 0 then
       Exit;
+    codepointLen:= abs( codepointLen);
     inc(p,codepointLen);
     dec(ByteCount,codepointLen);
   end;