diff --git a/ksh.spec b/ksh.spec
index 2ad3cf8..cceea53 100644
--- a/ksh.spec
+++ b/ksh.spec
@@ -186,7 +186,7 @@ sed -i '/-c sh\/main.c/s|${mam_cc_FLAGS} |${mam_cc_FLAGS} ${CCFLAGS} |p' src/cmd
 
 %build
 XTRAFLAGS=""
-for f in -Wno-unknown-pragmas -Wno-missing-braces -Wno-unused-result -Wno-return-type -Wno-int-to-pointer-cast -Wno-parentheses -Wno-unused -Wno-unused-but-set-variable -Wno-cpp
+for f in -Wno-unknown-pragmas -Wno-missing-braces -Wno-unused-result -Wno-return-type -Wno-int-to-pointer-cast -Wno-parentheses -Wno-unused -Wno-unused-but-set-variable -Wno-cpp -P
 do
   gcc $f -E - </dev/null >/dev/null 2>&1 && XTRAFLAGS="$XTRAFLAGS $f"
 done