diff --git a/spec/build/bsps/makecustom.yml b/spec/build/bsps/makecustom.yml
index 139629b597..9f5f2f2e59 100644
--- a/spec/build/bsps/makecustom.yml
+++ b/spec/build/bsps/makecustom.yml
@@ -2,7 +2,7 @@ SPDX-License-Identifier: CC-BY-SA-4.0 OR BSD-2-Clause
 build-type: config-file
 content: |
   include $$(RTEMS_ROOT)/make/custom/default.cfg
-  CPU_DEFINES = -I$$(exec_prefix)/$$(RTEMS_BSP)/lib/include
+  CPU_DEFINES = -isystem$$(exec_prefix)/$$(RTEMS_BSP)/lib/include
   CPU_CFLAGS = ${ABI_FLAGS}
   CFLAGS_OPTIMIZE_V = ${OPTIMIZATION_FLAGS}
   LDFLAGS = -B$$(exec_prefix)/$$(RTEMS_BSP)/lib ${PKGCONFIG_LDFLAGS}
diff --git a/spec/build/bsps/pkgconfig.yml b/spec/build/bsps/pkgconfig.yml
index a9462fcc95..8a3c3677a4 100644
--- a/spec/build/bsps/pkgconfig.yml
+++ b/spec/build/bsps/pkgconfig.yml
@@ -22,7 +22,7 @@ content: |
   Name: ${ARCH}-rtems${__RTEMS_MAJOR__}-${BSP_NAME}
   Version: ${RTEMS_VERSION}
   Description: RTEMS BSP ${ARCH}/${BSP_NAME}
-  Cflags: $${ABI_FLAGS} -I$${includedir}
+  Cflags: $${ABI_FLAGS} -isystem$${includedir}
   Ldflags: -B$${libdir} ${PKGCONFIG_LDFLAGS}
   Libs: -B$${libdir} ${PKGCONFIG_LDFLAGS}
 copyrights: