diff --git a/libtransmission/blocklist-test.c b/libtransmission/blocklist-test.c
index 4d01c0b65..3f443ec52 100644
--- a/libtransmission/blocklist-test.c
+++ b/libtransmission/blocklist-test.c
@@ -19,12 +19,14 @@
 #include "libtransmission-test.h"
 
 static char const* contents1 =
+    "10.5.6.7/8\n"
     "Austin Law Firm:216.16.1.144-216.16.1.151\n"
     "Sargent Controls and Aerospace:216.19.18.0-216.19.18.255\n"
     "Corel Corporation:216.21.157.192-216.21.157.223\n"
     "Fox Speed Channel:216.79.131.192-216.79.131.223\n";
 
 static char const* contents2 =
+    "10.5.6.7/8\n"
     "Austin Law Firm:216.16.1.144-216.16.1.151\n"
     "Sargent Controls and Aerospace:216.19.18.0-216.19.18.255\n"
     "Corel Corporation:216.21.157.192-216.21.157.223\n"
@@ -70,7 +72,7 @@ static int test_parsing(void)
     tr_free(path);
     tr_sessionReloadBlocklists(session);
     check(tr_blocklistExists(session));
-    check_int(tr_blocklistGetRuleCount(session), ==, 4);
+    check_int(tr_blocklistGetRuleCount(session), ==, 5);
 
     /* enable the blocklist */
     check(!tr_blocklistIsEnabled(session));
@@ -78,6 +80,8 @@ static int test_parsing(void)
     check(tr_blocklistIsEnabled(session));
 
     /* test blocked addresses */
+    check(!address_is_blocked(session, "0.0.0.1"));
+    check(address_is_blocked(session, "10.1.2.3"));
     check(!address_is_blocked(session, "216.16.1.143"));
     check(address_is_blocked(session, "216.16.1.144"));
     check(address_is_blocked(session, "216.16.1.145"));
@@ -116,22 +120,22 @@ static int test_updating(void)
     /* test that updated source files will get loaded */
     create_text_file(path, contents1);
     tr_sessionReloadBlocklists(session);
-    check_int(tr_blocklistGetRuleCount(session), ==, 4);
+    check_int(tr_blocklistGetRuleCount(session), ==, 5);
 
     /* test that updated source files will get loaded */
     create_text_file(path, contents2);
     tr_sessionReloadBlocklists(session);
-    check_int(tr_blocklistGetRuleCount(session), ==, 5);
+    check_int(tr_blocklistGetRuleCount(session), ==, 6);
 
     /* test that updated source files will get loaded */
     create_text_file(path, contents1);
     tr_sessionReloadBlocklists(session);
-    check_int(tr_blocklistGetRuleCount(session), ==, 4);
+    check_int(tr_blocklistGetRuleCount(session), ==, 5);
 
     /* ensure that new files, if bad, get skipped */
     create_text_file(path, "# nothing useful\n");
     tr_sessionReloadBlocklists(session);
-    check_int(tr_blocklistGetRuleCount(session), ==, 4);
+    check_int(tr_blocklistGetRuleCount(session), ==, 5);
 
     /* cleanup */
     libttest_session_close(session);
diff --git a/libtransmission/blocklist.c b/libtransmission/blocklist.c
index 434c999db..c6e37ae82 100644
--- a/libtransmission/blocklist.c
+++ b/libtransmission/blocklist.c
@@ -301,9 +301,38 @@ static bool parseLine2(char const* line, struct tr_ipv4_range* range)
     return true;
 }
 
+/*
+ * CIDR notation: "0.0.0.0/8", IPv4 only
+ * https://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing#CIDR_notation
+ */
+static bool parseLine3(char const* line, struct tr_ipv4_range* range) {
+    unsigned ip[4];
+    unsigned pflen;
+    uint32_t ip_u;
+    uint32_t mask = 0xffffffff;
+
+    if (sscanf(line, "%u.%u.%u.%u/%u", &ip[0], &ip[1], &ip[2], &ip[3], &pflen) != 5) {
+        return false;
+    }
+
+    if (pflen > 32 || ip[0] > 0xff || ip[1] > 0xff || ip[2] > 0xff || ip[3] > 0xff) {
+        return false;
+    }
+
+    /* this is host order */
+    mask <<= 32 - pflen;
+    ip_u = ip[0] << 24 | ip[1] << 16 | ip[2] << 8 | ip[3];
+
+    /* fill the non-prefix bits the way we need it */
+    range->begin = ip_u & mask;
+    range->end = ip_u | (~mask);
+
+    return true;
+}
+
 static bool parseLine(char const* line, struct tr_ipv4_range* range)
 {
-    return parseLine1(line, range) || parseLine2(line, range);
+    return parseLine1(line, range) || parseLine2(line, range) || parseLine3(line, range);
 }
 
 static int compareAddressRangesByFirstAddress(void const* va, void const* vb)