diff --git a/reactos/base/applications/calc/calc.h b/reactos/base/applications/calc/calc.h
index 1e645e75e84..3b36230b62a 100644
--- a/reactos/base/applications/calc/calc.h
+++ b/reactos/base/applications/calc/calc.h
@@ -1,4 +1,3 @@
-#pragma once
 
 #include <windows.h>
 #include <tchar.h>
diff --git a/reactos/base/applications/calc/calc.rbuild b/reactos/base/applications/calc/calc.rbuild
index 304a02e0c01..4cbc7869e3e 100644
--- a/reactos/base/applications/calc/calc.rbuild
+++ b/reactos/base/applications/calc/calc.rbuild
@@ -14,4 +14,5 @@
 	<file>utl.c</file>
 	<file>winmain.c</file>
 	<file>resource.rc</file>
+	<pch>calc.h</pch>
 </module>
diff --git a/reactos/base/applications/calc/fun_mpfr.c b/reactos/base/applications/calc/fun_mpfr.c
index e52193b6209..8d1534048a2 100644
--- a/reactos/base/applications/calc/fun_mpfr.c
+++ b/reactos/base/applications/calc/fun_mpfr.c
@@ -1,5 +1,4 @@
 #include "calc.h"
-#include <limits.h>
 
 void apply_int_mask(calc_number_t *r)
 {
diff --git a/reactos/base/applications/calc/function.c b/reactos/base/applications/calc/function.c
index 2da681ff26b..82bd6f46617 100644
--- a/reactos/base/applications/calc/function.c
+++ b/reactos/base/applications/calc/function.c
@@ -1,5 +1,4 @@
 #include "calc.h"
-#include <limits.h>
 
 void apply_int_mask(calc_number_t *r)
 {