diff --git a/src/util/util.c b/src/util/util.c
index 3c200d3680..cf1290dbc9 100644
--- a/src/util/util.c
+++ b/src/util/util.c
@@ -2390,7 +2390,13 @@ int virGetUserID(virConnectPtr conn,
     char *strbuf;
     struct passwd pwbuf;
     struct passwd *pw = NULL;
-    size_t strbuflen = sysconf(_SC_GETPW_R_SIZE_MAX);
+    long val = sysconf(_SC_GETPW_R_SIZE_MAX);
+    size_t strbuflen = val;
+
+    if (val < 0) {
+        virReportSystemError(conn, errno, "%s", _("sysconf failed"));
+        return -1;
+    }
 
     if (VIR_ALLOC_N(strbuf, strbuflen) < 0) {
         virReportOOMError(conn);
@@ -2427,7 +2433,13 @@ int virGetGroupID(virConnectPtr conn,
     char *strbuf;
     struct group grbuf;
     struct group *gr = NULL;
-    size_t strbuflen = sysconf(_SC_GETGR_R_SIZE_MAX);
+    long val = sysconf(_SC_GETGR_R_SIZE_MAX);
+    size_t strbuflen = val;
+
+    if (val < 0) {
+        virReportSystemError(conn, errno, "%s", _("sysconf failed"));
+        return -1;
+    }
 
     if (VIR_ALLOC_N(strbuf, strbuflen) < 0) {
         virReportOOMError(conn);