diff --git a/rtl/win64/signals.pp b/rtl/win64/signals.pp
index ce3bf86ec6..b806e25c13 100644
--- a/rtl/win64/signals.pp
+++ b/rtl/win64/signals.pp
@@ -345,6 +345,7 @@ interface
 
 implementation
 
+{$asmmode att}
 
 const
      EXCEPTION_ACCESS_VIOLATION = $c0000005;
diff --git a/rtl/win64/system.pp b/rtl/win64/system.pp
index 0cd5a6b173..6da6b2c9ef 100644
--- a/rtl/win64/system.pp
+++ b/rtl/win64/system.pp
@@ -100,6 +100,8 @@ Const
 
 implementation
 
+{$asmmode att}
+
 var
   SysInstance : qword;public;
 
diff --git a/rtl/x86_64/cpu.pp b/rtl/x86_64/cpu.pp
index 865560c135..ef0f448024 100644
--- a/rtl/x86_64/cpu.pp
+++ b/rtl/x86_64/cpu.pp
@@ -41,6 +41,8 @@ unit cpu;
 
   implementation
 
+{$asmmode att}
+
     var
       _AESSupport,
       _AVXSupport,