diff --git a/include/complex.h b/include/complex.h
index 414230472d2b..395983fab5c4 100644
--- a/include/complex.h
+++ b/include/complex.h
@@ -29,11 +29,15 @@
 #ifndef _COMPLEX_H
 #define	_COMPLEX_H
 
+#include <sys/cdefs.h>
+
 #ifdef __GNUC__
 #if __STDC_VERSION__ < 199901
 #define	_Complex	__complex__
 #endif
-#define	_Complex_I	1.0fi
+#define	_Complex_I	((float _Complex)1.0i)
+_Static_assert(__generic(_Complex_I, float _Complex, 1, 0),
+    "_Complex_I must be of type float _Complex");
 #endif
 
 #define	complex		_Complex