diff --git a/libutil/concat.c b/libutil/concat.c
index ef1e5b9..551b5b9 100644
--- a/libutil/concat.c
+++ b/libutil/concat.c
@@ -10,12 +10,13 @@ concat(FILE *fp1, const char *s1, FILE *fp2, const char *s2)
 	char buf[BUFSIZ];
 	size_t n;
 
-	while ((n = fread(buf, 1, sizeof(buf), fp1)) > 0) {
-		if (fwrite(buf, 1, n, fp2) != n)
-			eprintf("%s: write error:", s2);
-		if (feof(fp1))
+	while ((n = fread(buf, 1, sizeof(buf), fp1))) {
+		fwrite(buf, 1, n, fp2);
+		if (ferror(fp2))
+			eprintf("fwrite %s:", s2);
+		if (feof(fp1) || ferror(fp1))
 			break;
 	}
 	if (ferror(fp1))
-		eprintf("%s: read error:", s1);
+		eprintf("fread %s", s1);
 }