diff --git a/CHANGES b/CHANGES
index ea24f62022..fb77ce6736 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,5 @@
+4373.	[bug]		Address undefined behaviour in getaddrinfo. [RT #42479]
+
 4372.	[bug]		Address undefined behaviour in libt_api. [RT #42480]
 
 4371.	[func]		New "minimal-any" option reduces the size of UDP
diff --git a/lib/irs/getaddrinfo.c b/lib/irs/getaddrinfo.c
index e61602eb3e..aa0b4fe7c9 100644
--- a/lib/irs/getaddrinfo.c
+++ b/lib/irs/getaddrinfo.c
@@ -417,7 +417,7 @@ getaddrinfo(const char *hostname, const char *servname,
 				goto inet6_addr;
 			}
 			addrsize = sizeof(struct in_addr);
-			addroff = (char *)(&SIN(0)->sin_addr) - (char *)0;
+			addroff = offsetof(struct sockaddr_in, sin_addr);
 			family = AF_INET;
 			goto common;
 #ifdef IRS_HAVE_SIN6_SCOPE_ID
@@ -426,7 +426,7 @@ getaddrinfo(const char *hostname, const char *servname,
 			if (family && family != AF_INET6)
 				return (EAI_NONAME);
 			addrsize = sizeof(struct in6_addr);
-			addroff = (char *)(&SIN6(0)->sin6_addr) - (char *)0;
+			addroff = offsetof(struct sockaddr_in6, sin6_addr);
 			family = AF_INET6;
 			goto common;
 #endif
@@ -435,7 +435,7 @@ getaddrinfo(const char *hostname, const char *servname,
 				return (EAI_NONAME);
 		inet6_addr:
 			addrsize = sizeof(struct in6_addr);
-			addroff = (char *)(&SIN6(0)->sin6_addr) - (char *)0;
+			addroff = offsetof(struct sockaddr_in6, sin6_addr);
 			family = AF_INET6;
 
 		common: