1 files changed, 1 insertions, 0 deletions
diff --git a/math.c b/math.c
index 63a386360a..c7e79c1a80 100644
--- a/math.c
+++ b/math.c
@@ -15,6 +15,7 @@
 
 VALUE rb_mMath;
 
+extern VALUE rb_to_float(VALUE val);
 #define Need_Float(x) (x) = rb_to_float(x)
 #define Need_Float2(x,y) do {\
     Need_Float(x);\