diff --git a/snmp/snmp.c b/snmp/snmp.c
index f88d8a0..740b3aa 100644
--- a/snmp/snmp.c
+++ b/snmp/snmp.c
@@ -58,8 +58,12 @@ char *request(void *sessp, long max_repetitions, oid *name, size_t name_length,
 	if (status != STAT_SUCCESS) {
 		char *errstr = session_error(sessp);
 		char *err = NULL;
-		asprintf(&err, "SNMP request error: %s", errstr);
-		free(errstr);
+		int failure = asprintf(&err, "SNMP request error: %s", errstr);
+		if (failure == -1) {
+			err = errstr;
+		} else {
+			free(errstr);
+		}
 		return err;
 	}
 
@@ -119,8 +123,12 @@ struct bulkwalk_response *bulkwalk(char *peername, char *community) {
 	if ((sessp = snmp_sess_open(&session)) == NULL) {
 		char *errstr = open_error(&session);
 		char *err = NULL;
-		asprintf(&err, "Open SNMP session error: %s", errstr);
-		free(errstr);
+		int failure = asprintf(&err, "Open SNMP session error: %s", errstr);
+		if (failure == -1) {
+			err = errstr;
+		} else {
+			free(errstr);
+		}
 		add_error(response, err);
 		return response;
 	}
@@ -163,8 +171,12 @@ struct bulkwalk_response *bulkwalk(char *peername, char *community) {
 
 		char *errstr = session_error(sessp);
 		err = NULL;
-		asprintf(&err, "SNMP response error (%ld): %s", subtree->errstat, errstr);
-		free(errstr);
+		int failure = asprintf(&err, "SNMP response error (%ld): %s", subtree->errstat, errstr);
+		if (failure == -1) {
+			err = errstr;
+		} else {
+			free(errstr);
+		}
 		add_error(response, err);
 		snmp_free_pdu(subtree);
 		break;
diff --git a/snmp/snmp.h b/snmp/snmp.h
index aa2fd0c..f9c2c4e 100644
--- a/snmp/snmp.h
+++ b/snmp/snmp.h
@@ -6,6 +6,13 @@ license that can be found in the LICENSE file or at
 https://developers.google.com/open-source/licenses/bsd
 */
 
+// This makes asprintf work properly under GNU.
+#ifdef __GNUC__
+# ifndef _GNU_SOURCE
+#  define _GNU_SOURCE
+# endif // _GNU_SOURCE
+#endif //__GNUC__
+
 #include <stddef.h> // size_t
 #include <stdio.h>  // asprintf
 #include <stdlib.h> // calloc, realloc, free