diff --git a/src/system/libroot/posix/glibc/math/complex.h b/src/system/libroot/posix/glibc/math/complex.h
index f005a93912..448b0ca787 100644
--- a/src/system/libroot/posix/glibc/math/complex.h
+++ b/src/system/libroot/posix/glibc/math/complex.h
@@ -84,7 +84,7 @@ __BEGIN_DECLS
 
 /* And the long double versions.  It is non-critical to define them
    here unconditionally since `long double' is required in ISO C99.  */
-#if __STDC__ - 0 || __GNUC__ - 0 && !defined __NO_LONG_DOUBLE_MATH
+#if (__STDC__ - 0 || __GNUC__ - 0) && !defined __NO_LONG_DOUBLE_MATH
 # ifndef _Mlong_double_
 #  define _Mlong_double_	long double
 # endif