diff --git a/tests/fpc/encoding.pas b/tests/fpc/encoding.pas
index dd79589..0f6c57d 100644
--- a/tests/fpc/encoding.pas
+++ b/tests/fpc/encoding.pas
@@ -24,6 +24,7 @@   TTestEncoding = class(TTestCase)
     procedure IdWithInvalidCharacter;
     // out-of-range test not implemented:
     // compiler enforces that all numbers are within the range of a TNumber
+    procedure ExtremeValue;
   end;
 
 implementation
@@ -189,6 +190,20 @@ procedure TTestEncoding.IdWithInvalidCharacter;
   end;
 end;
 
+procedure TTestEncoding.ExtremeValue;
+const
+  Number: TNumber = $FFFFFFFFFFFFFFFF;
+  Id = 'eIkvoXH40Lmd'; // from a previous EncodeSingle
+begin
+  with TSqids.Create do
+  try
+    AssertEquals(EncodeSingle(Number), Id);
+    AssertTrue(DecodeSingle(Id) = Number);
+  finally
+    Free;
+  end;
+end;
+
 initialization
   RegisterTest(TTestEncoding);
 
diff --git a/tests/fpc/testsqids.lpi b/tests/fpc/testsqids.lpi
index 43f1174..3f0347a 100644
--- a/tests/fpc/testsqids.lpi
+++ b/tests/fpc/testsqids.lpi
@@ -1,16 +1,16 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <CONFIG>
   <ProjectOptions>
-    <Version Value="11"/>
+    <Version Value="12"/>
     <PathDelim Value="\"/>
     <General>
       <Flags>
         <MainUnitHasCreateFormStatements Value="False"/>
         <MainUnitHasTitleStatement Value="False"/>
         <MainUnitHasScaledStatement Value="False"/>
+        <CompatibilityMode Value="True"/>
       </Flags>
       <SessionStorage Value="InProjectDir"/>
-      <MainUnit Value="0"/>
       <Title Value="testsqids"/>
       <UseAppBundle Value="False"/>
       <ResourceType Value="res"/>
@@ -24,7 +24,6 @@
     </PublishOptions>
     <RunParams>
       <FormatVersion Value="2"/>
-      <Modes Count="0"/>
     </RunParams>
     <RequiredPackages Count="1">
       <Item1>