diff --git a/tools/winapi/winapi.pm b/tools/winapi/winapi.pm
index dcd92680daa..928476db886 100644
--- a/tools/winapi/winapi.pm
+++ b/tools/winapi/winapi.pm
@@ -281,7 +281,7 @@ sub parse_spec_file($$) {
 	my $ordinal;
 	my $ARCHES="alpha|i386|powerpc|sparc|win32|win64|x86_64";
 	if(/^(\d+|@)\s+
-	   (cdecl|pascal|stdcall|varargs)\s+
+	   (cdecl|pascal|stdcall|varargs|thiscall)\s+
 	   ((?:(?:-arch=(?:$ARCHES)(?:,(?:$ARCHES))*|-noname|-norelay|-ordinal|-i386|-ret16|-ret64|-register|-interrupt|-private)\s+)*)(\S+)\s*\(\s*(.*?)\s*\)\s*(\S*)$/x)
 	{
 	    my $calling_convention = $2;