Index: uspace/lib/posix/stdbool.h
===================================================================
--- uspace/lib/posix/stdbool.h	(revision 097f4219b7d1531776dbf497f0508aed611d45a5)
+++ uspace/lib/posix/stdbool.h	(revision 341b5155553dd6d613629bd6d5bc76474f5692e8)
@@ -37,10 +37,11 @@
 
 #ifdef LIBC_BOOL_H_
-#	ifndef POSIX_STDIO_H_
-#		ifndef POSIX_STDLIB_H_
-#			error "You can't include bool.h and stdbool.h at the same time."
-#		endif
-#	endif
+#if (!defined(POSIX_STDIO_H_)) \
+		&& (!defined(POSIX_STDLIB_H_)) \
+		&& (!defined(POSIX_STRING_H_))
+#error "You can't include bool.h and stdbool.h at the same time."
 #endif
+#endif
+
 #define LIBC_BOOL_H_