diff --git a/src/win32/posix.h b/src/win32/posix.h
index 5f924a026..24cba23e0 100644
--- a/src/win32/posix.h
+++ b/src/win32/posix.h
@@ -12,6 +12,13 @@
 #include "utf-conv.h"
 #include "dir.h"
 
+/* define some standard errnos that the runtime may be missing.  for example,
+ * mingw lacks EAFNOSUPPORT. */
+
+#ifndef EAFNOSUPPORT
+# define EAFNOSUPPORT (INT_MAX-1)
+#endif
+
 GIT_INLINE(int) p_link(const char *old, const char *new)
 {
 	GIT_UNUSED(old);
diff --git a/src/win32/posix_w32.c b/src/win32/posix_w32.c
index 087adcce3..2f490529c 100644
--- a/src/win32/posix_w32.c
+++ b/src/win32/posix_w32.c
@@ -518,44 +518,40 @@ p_gmtime_r (const time_t *timer, struct tm *result)
 	return result;
 }
 
-int p_inet_pton(int af, const char* src, void* dst)
+int p_inet_pton(int af, const char *src, void *dst)
 {
-	union {
-		struct sockaddr_in6 sin6;
-		struct sockaddr_in sin;
-	} sa;
-	int srcsize;
+	struct sockaddr_storage sin;
+	void *addr;
+	int sin_len = sizeof(struct sockaddr_storage), addr_len;
+	int error = 0;
 
-	switch(af)
-	{
-		case AF_INET:
-			sa.sin.sin_family = AF_INET;
-			srcsize = (int)sizeof(sa.sin);
-		break;
-		case AF_INET6:
-			sa.sin6.sin6_family = AF_INET6;
-			srcsize = (int)sizeof(sa.sin6);
-		break;
-		default:
-			errno = WSAEPFNOSUPPORT;
-			return -1;
-	}
-
-	if (WSAStringToAddress((LPSTR)src, af, NULL, (struct sockaddr *) &sa, &srcsize) != 0)
-	{
-		errno = WSAGetLastError();
+	if (af == AF_INET) {
+		addr = &((struct sockaddr_in *)&sin)->sin_addr;
+		addr_len = sizeof(struct in_addr);
+	} else if (af == AF_INET6) {
+		addr = &((struct sockaddr_in6 *)&sin)->sin6_addr;
+		addr_len = sizeof(struct in6_addr);
+	} else {
+		errno = EAFNOSUPPORT;
 		return -1;
 	}
 
-	switch(af)
-	{
-		case AF_INET:
-			memcpy(dst, &sa.sin.sin_addr, sizeof(sa.sin.sin_addr));
-		break;
-		case AF_INET6:
-			memcpy(dst, &sa.sin6.sin6_addr, sizeof(sa.sin6.sin6_addr));
-		break;
+	if ((error = WSAStringToAddressA((LPSTR)src, af, NULL, (LPSOCKADDR)&sin, &sin_len)) == 0) {
+		memcpy(dst, addr, addr_len);
+		return 1;
 	}
 
-	return 1;
+	switch(WSAGetLastError()) {
+	case WSAEINVAL:
+		return 0;
+	case WSAEFAULT:
+		errno = ENOSPC;
+		return -1;
+	case WSA_NOT_ENOUGH_MEMORY:
+		errno = ENOMEM;
+		return -1;
+	}
+
+	errno = EINVAL;
+	return -1;
 }
diff --git a/tests-clar/core/posix.c b/tests-clar/core/posix.c
new file mode 100644
index 000000000..0d9443f92
--- /dev/null
+++ b/tests-clar/core/posix.c
@@ -0,0 +1,84 @@
+#ifndef _WIN32
+# include <arpa/inet.h>
+#else
+# include <ws2tcpip.h>
+# ifdef _MSC_VER
+#  pragma comment(lib, "ws2_32")
+# endif
+#endif
+
+#include "clar_libgit2.h"
+#include "posix.h"
+
+void test_core_posix__initialize(void)
+{
+#ifdef GIT_WIN32
+	/* on win32, the WSA context needs to be initialized
+	 * before any socket calls can be performed */
+	WSADATA wsd;
+
+	cl_git_pass(WSAStartup(MAKEWORD(2,2), &wsd));
+	cl_assert(LOBYTE(wsd.wVersion) == 2 && HIBYTE(wsd.wVersion) == 2);
+#endif
+}
+
+void test_core_posix__inet_pton(void)
+{
+	struct in_addr addr;
+	struct in6_addr addr6;
+	size_t i;
+	
+	struct in_addr_data {
+		const char *p;
+		const uint8_t n[4];
+	};
+
+	struct in6_addr_data {
+		const char *p;
+		const uint8_t n[16];
+	};
+
+	static struct in_addr_data in_addr_data[] = {
+		{ "0.0.0.0", { 0, 0, 0, 0 } },
+		{ "10.42.101.8", { 10, 42, 101, 8 } },
+		{ "127.0.0.1", { 127, 0, 0, 1 } },
+		{ "140.177.10.12", { 140, 177, 10, 12 } },
+		{ "204.232.175.90", { 204, 232, 175, 90 } },
+		{ "255.255.255.255", { 255, 255, 255, 255 } },
+	};
+
+	static struct in6_addr_data in6_addr_data[] = {
+		{ "::", { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 } },
+		{ "::1", { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01 } },
+		{ "0:0:0:0:0:0:0:1", { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01 } },
+		{ "2001:db8:8714:3a90::12", { 0x20, 0x01, 0x0d, 0xb8, 0x87, 0x14, 0x3a, 0x90, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x12 } },
+		{ "fe80::f8ba:c2d6:86be:3645", { 0xfe, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xf8, 0xba, 0xc2, 0xd6, 0x86, 0xbe, 0x36, 0x45 } },
+		{ "::ffff:204.152.189.116", { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0xff, 0xff, 0xcc, 0x98, 0xbd, 0x74 } },
+	};
+
+	/* Test some ipv4 addresses */
+	for (i = 0; i < 6; i++) {
+		cl_assert(p_inet_pton(AF_INET, in_addr_data[i].p, &addr) == 1);
+		cl_assert(memcmp(&addr, in_addr_data[i].n, sizeof(struct in_addr)) == 0);
+	}
+
+	/* Test some ipv6 addresses */
+	for (i = 0; i < 6; i++) {
+		cl_assert(p_inet_pton(AF_INET6, in6_addr_data[i].p, &addr6) == 1);
+		cl_assert(memcmp(&addr6, in6_addr_data[i].n, sizeof(struct in6_addr)) == 0);
+	}
+
+	/* Test some invalid strings */
+	cl_assert(p_inet_pton(AF_INET, "", &addr) == 0);
+	cl_assert(p_inet_pton(AF_INET, "foo", &addr) == 0);
+	cl_assert(p_inet_pton(AF_INET, " 127.0.0.1", &addr) == 0);
+	cl_assert(p_inet_pton(AF_INET, "bar", &addr) == 0);
+	cl_assert(p_inet_pton(AF_INET, "10.foo.bar.1", &addr) == 0);
+
+	/* Test unsupported address families */
+	cl_git_fail(p_inet_pton(12, "52.472", NULL)); /* AF_DECnet */
+	cl_assert_equal_i(EAFNOSUPPORT, errno);
+
+	cl_git_fail(p_inet_pton(5, "315.124", NULL)); /* AF_CHAOS */
+	cl_assert_equal_i(EAFNOSUPPORT, errno);
+}