diff --git a/src/libstore-tests/data/store-reference/ssh_unbracketed_ipv6_1.txt b/src/libstore-tests/data/store-reference/ssh_unbracketed_ipv6_1.txt
new file mode 100644
index 000000000..861b5bb35
--- /dev/null
+++ b/src/libstore-tests/data/store-reference/ssh_unbracketed_ipv6_1.txt
@@ -0,0 +1 @@
+ssh://::1
\ No newline at end of file
diff --git a/src/libstore-tests/data/store-reference/ssh_unbracketed_ipv6_2.txt b/src/libstore-tests/data/store-reference/ssh_unbracketed_ipv6_2.txt
new file mode 100644
index 000000000..952d5a55d
--- /dev/null
+++ b/src/libstore-tests/data/store-reference/ssh_unbracketed_ipv6_2.txt
@@ -0,0 +1 @@
+ssh://userinfo@fea5:23e1:3916:fc24:cb52:2837:2ecb:ea8e
\ No newline at end of file
diff --git a/src/libstore-tests/data/store-reference/ssh_unbracketed_ipv6_3.txt b/src/libstore-tests/data/store-reference/ssh_unbracketed_ipv6_3.txt
new file mode 100644
index 000000000..d1f17adac
--- /dev/null
+++ b/src/libstore-tests/data/store-reference/ssh_unbracketed_ipv6_3.txt
@@ -0,0 +1 @@
+ssh://userinfo@fea5:23e1:3916:fc24:cb52:2837:2ecb:ea8e?a=b&c=d
\ No newline at end of file
diff --git a/src/libstore-tests/store-reference.cc b/src/libstore-tests/store-reference.cc
index d9f040ab6..7b42b45a2 100644
--- a/src/libstore-tests/store-reference.cc
+++ b/src/libstore-tests/store-reference.cc
@@ -148,4 +148,39 @@ URI_TEST(
         .params = {},
     }))
 
+static StoreReference sshLoopbackIPv6{
+    .variant =
+        StoreReference::Specified{
+            .scheme = "ssh",
+            .authority = "[::1]",
+        },
+};
+
+URI_TEST_READ(ssh_unbracketed_ipv6_1, sshLoopbackIPv6)
+
+static StoreReference sshIPv6AuthorityWithUserinfo{
+    .variant =
+        StoreReference::Specified{
+            .scheme = "ssh",
+            .authority = "userinfo@[fea5:23e1:3916:fc24:cb52:2837:2ecb:ea8e]",
+        },
+};
+
+URI_TEST_READ(ssh_unbracketed_ipv6_2, sshIPv6AuthorityWithUserinfo)
+
+static StoreReference sshIPv6AuthorityWithUserinfoAndParams{
+    .variant =
+        StoreReference::Specified{
+            .scheme = "ssh",
+            .authority = "userinfo@[fea5:23e1:3916:fc24:cb52:2837:2ecb:ea8e]",
+        },
+    .params =
+        {
+            {"a", "b"},
+            {"c", "d"},
+        },
+};
+
+URI_TEST_READ(ssh_unbracketed_ipv6_3, sshIPv6AuthorityWithUserinfoAndParams)
+
 } // namespace nix
diff --git a/src/libstore/meson.build b/src/libstore/meson.build
index 253152772..7aeacbab7 100644
--- a/src/libstore/meson.build
+++ b/src/libstore/meson.build
@@ -105,6 +105,7 @@ boost = dependency(
     'container',
     # Shouldn't list, because can header-only, and Meson currently looks for libs
     #'regex',
+    'url',
   ],
   include_type : 'system',
 )
diff --git a/src/libstore/store-reference.cc b/src/libstore/store-reference.cc
index 2c54e497e..96ee829d0 100644
--- a/src/libstore/store-reference.cc
+++ b/src/libstore/store-reference.cc
@@ -1,11 +1,12 @@
-#include <regex>
-
 #include "nix/util/error.hh"
+#include "nix/util/split.hh"
 #include "nix/util/url.hh"
 #include "nix/store/store-reference.hh"
 #include "nix/util/file-system.hh"
 #include "nix/util/util.hh"
 
+#include <boost/url/ipv6_address.hpp>
+
 namespace nix {
 
 static bool isNonUriPath(const std::string & spec)
@@ -43,6 +44,29 @@ std::string StoreReference::render(bool withParams) const
     return res;
 }
 
+namespace {
+
+struct SchemeAndAuthorityWithPath
+{
+    std::string_view scheme;
+    std::string_view authority;
+};
+
+} // namespace
+
+/**
+ * Return the 'scheme' and remove the '://' or ':' separator.
+ */
+static std::optional<SchemeAndAuthorityWithPath> splitSchemePrefixTo(std::string_view string)
+{
+    auto scheme = splitPrefixTo(string, ':');
+    if (!scheme)
+        return std::nullopt;
+
+    splitPrefix(string, "//");
+    return SchemeAndAuthorityWithPath{.scheme = *scheme, .authority = string};
+}
+
 StoreReference StoreReference::parse(const std::string & uri, const StoreReference::Params & extraParams)
 {
     auto params = extraParams;
@@ -90,6 +114,32 @@ StoreReference StoreReference::parse(const std::string & uri, const StoreReferen
                     },
                 .params = std::move(params),
             };
+        } else if (auto schemeAndAuthority = splitSchemePrefixTo(baseURI)) {
+            /* Back-compatibility shim to accept unbracketed IPv6 addresses after the scheme.
+             * Old versions of nix allowed that. Note that this is ambiguous and does not allow
+             * specifying the port number. For that the address must be bracketed, otherwise it's
+             * greedily assumed to be the part of the host address. */
+            auto authorityString = schemeAndAuthority->authority;
+            auto userinfo = splitPrefixTo(authorityString, '@');
+            auto maybeIpv6 = boost::urls::parse_ipv6_address(authorityString);
+            if (maybeIpv6) {
+                std::string fixedAuthority;
+                if (userinfo) {
+                    fixedAuthority += *userinfo;
+                    fixedAuthority += '@';
+                }
+                fixedAuthority += '[';
+                fixedAuthority += authorityString;
+                fixedAuthority += ']';
+                return {
+                    .variant =
+                        Specified{
+                            .scheme = std::string(schemeAndAuthority->scheme),
+                            .authority = fixedAuthority,
+                        },
+                    .params = std::move(params),
+                };
+            }
         }
     }