diff --git a/lib/irs/getaddrinfo.c b/lib/irs/getaddrinfo.c
index 1b2df6d71c9a3df0e75c1f336833a136e0d6a06c..d5481c7afa605880b7c9e5ca17815d5f80e6ea5a 100644
--- a/lib/irs/getaddrinfo.c
+++ b/lib/irs/getaddrinfo.c
@@ -181,6 +181,47 @@ static void _freeaddrinfo(struct addrinfo *ai);
 #define FOUND_IPV6	0x2
 #define FOUND_MAX	2
 
+/*%
+ * Try converting the scope identifier in 'src' to a network interface index.
+ * Upon success, return true and store the resulting index in 'dst'.  Upon
+ * failure, return false.
+ */
+static bool
+parse_scopeid(const char *src, uint32_t *dst) {
+	uint32_t scopeid = 0;
+
+	REQUIRE(src != NULL);
+	REQUIRE(dst != NULL);
+
+#ifdef HAVE_IF_NAMETOINDEX
+	/*
+	 * Try using if_nametoindex() first if it is available.  As it does not
+	 * handle numeric scopes, we do not simply return if it fails.
+	 */
+	scopeid = (uint32_t)if_nametoindex(src);
+#endif
+
+	/*
+	 * Fall back to numeric scope processing if if_nametoindex() either
+	 * fails or is unavailable.
+	 */
+	if (scopeid == 0) {
+		char *endptr = NULL;
+		scopeid = (uint32_t)strtoul(src, &endptr, 10);
+		/*
+		 * The scope identifier must not be empty and no trailing
+		 * characters are allowed after it.
+		 */
+		if (src == endptr || endptr == NULL || *endptr != '\0') {
+			return (false);
+		}
+	}
+
+	*dst = scopeid;
+
+	return (true);
+}
+
 #define ISC_AI_MASK (AI_PASSIVE|AI_CANONNAME|AI_NUMERICHOST)
 /*%
  * Get a list of IP addresses and port numbers for host hostname and
@@ -365,39 +406,24 @@ getaddrinfo(const char *hostname, const char *servname,
 		char abuf[sizeof(struct in6_addr)];
 		char nbuf[NI_MAXHOST];
 		int addrsize, addroff;
-#ifdef IRS_HAVE_SIN6_SCOPE_ID
-		char *p, *ep;
 		char ntmp[NI_MAXHOST];
-		uint32_t scopeid;
-#endif
+		uint32_t scopeid = 0;
 
-#ifdef IRS_HAVE_SIN6_SCOPE_ID
 		/*
 		 * Scope identifier portion.
 		 */
 		ntmp[0] = '\0';
 		if (strchr(hostname, '%') != NULL) {
+			char *p;
 			strlcpy(ntmp, hostname, sizeof(ntmp));
 			p = strchr(ntmp, '%');
-			ep = NULL;
-
-			/*
-			 * Vendors may want to support non-numeric
-			 * scopeid around here.
-			 */
 
-			if (p != NULL)
-				scopeid = (uint32_t)strtoul(p + 1,
-								&ep, 10);
-			if (p != NULL && ep != NULL && ep[0] == '\0')
+			if (p != NULL && parse_scopeid(p + 1, &scopeid)) {
 				*p = '\0';
-			else {
+			} else {
 				ntmp[0] = '\0';
-				scopeid = 0;
 			}
-		} else
-			scopeid = 0;
-#endif
+		}
 
 		if (inet_pton(AF_INET, hostname, (struct in_addr *)abuf)
 		    == 1) {
@@ -415,7 +441,6 @@ getaddrinfo(const char *hostname, const char *servname,
 			addroff = offsetof(struct sockaddr_in, sin_addr);
 			family = AF_INET;
 			goto common;
-#ifdef IRS_HAVE_SIN6_SCOPE_ID
 		} else if (ntmp[0] != '\0' &&
 			   inet_pton(AF_INET6, ntmp, abuf) == 1) {
 			if (family && family != AF_INET6)
@@ -424,7 +449,6 @@ getaddrinfo(const char *hostname, const char *servname,
 			addroff = offsetof(struct sockaddr_in6, sin6_addr);
 			family = AF_INET6;
 			goto common;
-#endif
 		} else if (inet_pton(AF_INET6, hostname, abuf) == 1) {
 			if (family != 0 && family != AF_INET6)
 				return (EAI_NONAME);
@@ -444,12 +468,10 @@ getaddrinfo(const char *hostname, const char *servname,
 			ai->ai_socktype = socktype;
 			SIN(ai->ai_addr)->sin_port = port;
 			memmove((char *)ai->ai_addr + addroff, abuf, addrsize);
+			if (ai->ai_family == AF_INET6) {
+				SIN6(ai->ai_addr)->sin6_scope_id = scopeid;
+			}
 			if ((flags & AI_CANONNAME) != 0) {
-#ifdef IRS_HAVE_SIN6_SCOPE_ID
-				if (ai->ai_family == AF_INET6)
-					SIN6(ai->ai_addr)->sin6_scope_id =
-						scopeid;
-#endif
 				if (getnameinfo(ai->ai_addr,
 						(socklen_t)ai->ai_addrlen,
 						nbuf, sizeof(nbuf), NULL, 0,