diff --git a/reactos/lib/cmlib/cmlib.h b/reactos/lib/cmlib/cmlib.h
index 03d3851bd53..cb81c53a5b1 100644
--- a/reactos/lib/cmlib/cmlib.h
+++ b/reactos/lib/cmlib/cmlib.h
@@ -48,6 +48,10 @@
     KeQuerySystemTime(
         OUT PLARGE_INTEGER CurrentTime);
 
+    WCHAR NTAPI
+    RtlUpcaseUnicodeChar(
+        IN WCHAR Source);
+
     VOID NTAPI
     RtlInitializeBitMap(
         IN PRTL_BITMAP BitMapHeader,