diff --git a/package/ruby/ruby.mk b/package/ruby/ruby.mk
index 4c6459b74c..f0dc63b471 100644
--- a/package/ruby/ruby.mk
+++ b/package/ruby/ruby.mk
@@ -29,6 +29,17 @@ RUBY_CFLAGS += -O2
 endif
 RUBY_CONF_ENV = CFLAGS="$(RUBY_CFLAGS)"
 
+ifeq ($(BR2_TOOLCHAIN_USES_UCLIBC),y)
+# On uClibc, finite, isinf and isnan are not directly implemented as
+# functions.  Instead math.h #define's these to __finite, __isinf and
+# __isnan, confusing the Ruby configure script. Tell it that they
+# really are available.
+RUBY_CONF_ENV += \
+	ac_cv_func_finite=yes \
+	ac_cv_func_isinf=yes \
+	ac_cv_func_isnan=yes
+endif
+
 ifeq ($(BR2_bfin),y)
 RUBY_CONF_ENV += ac_cv_func_dl_iterate_phdr=no
 # Blackfin doesn't have FFI closure support, needed by the fiddle