diff --git a/mrbgems/mruby-cmath/src/cmath.c b/mrbgems/mruby-cmath/src/cmath.c
index 8b0c4d04a..de59adf96 100644
--- a/mrbgems/mruby-cmath/src/cmath.c
+++ b/mrbgems/mruby-cmath/src/cmath.c
@@ -92,7 +92,7 @@ CXDIVc(mrb_complex a, mrb_complex b)
 
 #else
 
-#if defined(__cplusplus) && defined(__APPLE__)
+#if defined(__cplusplus) && (defined(__APPLE__) || (defined(__clang__) && (defined(__FreeBSD__) || defined(__OpenBSD__))))
 
 #ifdef MRB_USE_FLOAT32
 typedef std::complex<float> mrb_complex;