diff --git a/package/uclibc/uClibc-ng.config b/package/uclibc/uClibc-ng.config
index 66de5a92a9..2671e06777 100644
--- a/package/uclibc/uClibc-ng.config
+++ b/package/uclibc/uClibc-ng.config
@@ -1,4 +1,5 @@
 DO_C99_MATH=y
+DO_XSI_MATH=y
 KERNEL_HEADERS="/usr/src/linux/include"
 # LDSO_CACHE_SUPPORT is not set
 # UCLIBC_STATIC_LDCONFIG is not set