diff --git a/src/numeric.c b/src/numeric.c
index 45b37451e..109833bb9 100644
--- a/src/numeric.c
+++ b/src/numeric.c
@@ -20,10 +20,12 @@
 #endif
 #endif
 
+#ifdef MRB_USE_COMPLEX
 mrb_value mrb_complex_new(mrb_state *mrb, mrb_float x, mrb_float y);
 mrb_value mrb_complex_add(mrb_state *mrb, mrb_value x, mrb_value y);
 mrb_value mrb_complex_sub(mrb_state *mrb, mrb_value x, mrb_value y);
 mrb_value mrb_complex_mul(mrb_state *mrb, mrb_value x, mrb_value y);
+#endif
 
 mrb_value mrb_rational_new(mrb_state *mrb, mrb_int x, mrb_int y);
 mrb_value mrb_rational_add(mrb_state *mrb, mrb_value x, mrb_value y);
diff --git a/src/numops.c b/src/numops.c
index 97fa81186..f98aa418c 100644
--- a/src/numops.c
+++ b/src/numops.c
@@ -12,10 +12,12 @@ mrb_value mrb_int_add(mrb_state *mrb, mrb_value x, mrb_value y);
 mrb_value mrb_int_sub(mrb_state *mrb, mrb_value x, mrb_value y);
 mrb_value mrb_int_mul(mrb_state *mrb, mrb_value x, mrb_value y);
 
+#ifdef MRB_USE_COMPLEX
 mrb_value mrb_complex_new(mrb_state *mrb, mrb_float x, mrb_float y);
 mrb_value mrb_complex_add(mrb_state *mrb, mrb_value x, mrb_value y);
 mrb_value mrb_complex_sub(mrb_state *mrb, mrb_value x, mrb_value y);
 mrb_value mrb_complex_mul(mrb_state *mrb, mrb_value x, mrb_value y);
+#endif
 
 mrb_value mrb_rational_new(mrb_state *mrb, mrb_int x, mrb_int y);
 mrb_value mrb_rational_add(mrb_state *mrb, mrb_value x, mrb_value y);