diff --git a/mx_util.c b/mx_util.c
index 52e890de..7f99daf2 100644
--- a/mx_util.c
+++ b/mx_util.c
@@ -1360,7 +1360,7 @@ static char *mx_call_external_v(char *helper, char **argv) {
         goto err_close;
     }
     if (len == sizeof(buf)) {
-        err = EPIPE;
+        err = EPROTO;
         goto err_close;
     }
 
@@ -1369,7 +1369,7 @@ static char *mx_call_external_v(char *helper, char **argv) {
     int wstatus;
     waitpid(pid, &wstatus, 0);
     if (wstatus != 0) {
-        err = EPIPE;
+        err = EPROTO;
         goto err_err;
     }
     buf[len] = '\0';
diff --git a/test_mx_util.c b/test_mx_util.c
index e55d0070..028a9ebb 100644
--- a/test_mx_util.c
+++ b/test_mx_util.c
@@ -545,13 +545,13 @@ static void test_mx_call_external() {
     assert(errno == 999);
 
     line = mx_call_external("/usr/bin/false", NULL);
-    assert(line == NULL && errno==EPIPE);
+    assert(line == NULL && errno==EPROTO);
 
     line = mx_call_external("/usr/bin/cat", "/usr/bin/bash", NULL);
-    assert(line == NULL && errno==EPIPE);
+    assert(line == NULL && errno==EPROTO);
 
     line = mx_call_external("/usr/bin/yes", NULL);
-    assert(line == NULL && errno==EPIPE);
+    assert(line == NULL && errno==EPROTO);
 
 }