diff --git a/src/layer/unaryop.cpp b/src/layer/unaryop.cpp
index c86584e3985..28447f171e7 100644
--- a/src/layer/unaryop.cpp
+++ b/src/layer/unaryop.cpp
@@ -108,7 +108,7 @@ struct unary_op_exp
 {
     float operator()(const float& x) const
     {
-        return (float)exp(x);
+        return (float)expf(x);
     }
 };