diff --git a/Makefile.inc1 b/Makefile.inc1
index 92d89e1f77a8..e204553dd7ad 100644
--- a/Makefile.inc1
+++ b/Makefile.inc1
@@ -637,7 +637,8 @@ XCFLAGS+=	-isystem ${WORLDTMP}/usr/include -L${WORLDTMP}/usr/lib
 # combined with --sysroot.
 XCFLAGS+=	-B${WORLDTMP}/usr/lib
 # Force using libc++ for external GCC.
-.if ${X_COMPILER_TYPE} == gcc && ${X_COMPILER_VERSION} >= 40800
+.if defined(X_COMPILER_TYPE) && \
+    ${X_COMPILER_TYPE} == gcc && ${X_COMPILER_VERSION} >= 40800
 XCXXFLAGS+=	-isystem ${WORLDTMP}/usr/include/c++/v1 -std=c++11 \
 		-nostdinc++
 .endif
@@ -2880,7 +2881,8 @@ CD2CFLAGS+=	-isystem ${XDDESTDIR}/usr/include -L${XDDESTDIR}/usr/lib
 # combined with --sysroot.
 CD2CFLAGS+=	-B${XDDESTDIR}/usr/lib
 # Force using libc++ for external GCC.
-.if ${X_COMPILER_TYPE} == gcc && ${X_COMPILER_VERSION} >= 40800
+.if defined(X_COMPILER_TYPE) && \
+    ${X_COMPILER_TYPE} == gcc && ${X_COMPILER_VERSION} >= 40800
 CD2CXXFLAGS+=	-isystem ${XDDESTDIR}/usr/include/c++/v1 -std=c++11 \
 		-nostdinc++
 .endif
diff --git a/Makefile.libcompat b/Makefile.libcompat
index dda1a29f50d5..35d804e9f650 100644
--- a/Makefile.libcompat
+++ b/Makefile.libcompat
@@ -108,7 +108,8 @@ LIBCOMPATCFLAGS+=	-B${LIBCOMPATTMP}/usr/lib${libcompat}
 # sysroot path which --sysroot does not actually do for headers.
 LIBCOMPATCFLAGS+=	-isystem ${LIBCOMPATTMP}/usr/include
 # Force using libc++ for external GCC.
-.if ${X_COMPILER_TYPE} == gcc && ${X_COMPILER_VERSION} >= 40800 && \
+.if defined(X_COMPILER_TYPE) && \
+    ${X_COMPILER_TYPE} == gcc && ${X_COMPILER_VERSION} >= 40800 && \
     (${MK_CLANG_BOOTSTRAP} == "no" && ${MK_GCC_BOOTSTRAP} == "no")
 LIBCOMPATCXXFLAGS+=	-isystem ${LIBCOMPATTMP}/usr/include/c++/v1 -std=c++11 \
 			-nostdinc++