diff --git a/lang/cem/libcc.ansi/math/ldexp.c b/lang/cem/libcc.ansi/math/ldexp.c
index dd704df99..5ec83a8fd 100644
--- a/lang/cem/libcc.ansi/math/ldexp.c
+++ b/lang/cem/libcc.ansi/math/ldexp.c
@@ -6,6 +6,7 @@
 
 #include	<math.h>
 #include	<float.h>
+#include	<errno.h>
 
 double
 ldexp(double fl, int exp)
@@ -22,6 +23,7 @@ ldexp(double fl, int exp)
 	exp += currexp;
 	if (exp > 0) {
 		if (exp > DBL_MAX_EXP) {
+			errno = ERANGE;
 			return sign * HUGE_VAL;
 		}
 		while (exp>30) {