diff --git a/libm/fake_long_double.c b/libm/fake_long_double.c
index 751911a1b..756e35bab 100644
--- a/libm/fake_long_double.c
+++ b/libm/fake_long_double.c
@@ -31,7 +31,7 @@ int (isnanf)(float a1) { return __isnanf(a1); }
 int __fpclassifyl(long double a1) { return __fpclassifyd(a1); }
 int __isfinitel(long double a1) { return __isfinite(a1); }
 int __isinfl(long double a1) { return __isinf(a1); }
-int __isnanl(long double a1) { return isnan(a1); }
+int __isnanl(long double a1) { return (isnan)(a1); }
 int __isnormall(long double a1) { return __isnormal(a1); }
 int __signbitl(long double a1) { return __signbit(a1); }