diff --git a/src/libstore/ssh.cc b/src/libstore/ssh.cc
index 116a480ba..f47cfbbec 100644
--- a/src/libstore/ssh.cc
+++ b/src/libstore/ssh.cc
@@ -240,4 +240,19 @@ Path SSHMaster::startMaster()
 
 #endif
 
+void SSHMaster::Connection::trySetBufferSize(size_t size)
+{
+#ifdef F_SETPIPE_SZ
+    /* This `fcntl` method of doing this takes a positive `int`. Check
+       and convert accordingly.
+
+       The function overall still takes `size_t` because this is more
+       portable for a platform-agnostic interface. */
+    assert(size <= INT_MAX);
+    int pipesize = size;
+    fcntl(in.get(), F_SETPIPE_SZ, pipesize);
+    fcntl(out.get(), F_SETPIPE_SZ, pipesize);
+#endif
+}
+
 }
diff --git a/src/libstore/ssh.hh b/src/libstore/ssh.hh
index 85be704ec..eb05df011 100644
--- a/src/libstore/ssh.hh
+++ b/src/libstore/ssh.hh
@@ -54,6 +54,18 @@ public:
         Pid sshPid;
 #endif
         AutoCloseFD out, in;
+
+        /**
+         * Try to set the buffer size in both directions to the
+         * designated amount, if possible. If not possible, does
+         * nothing.
+         *
+         * Current implementation is to use `fcntl` with `F_SETPIPE_SZ`,
+         * which is Linux-only. For this implementation, `size` must
+         * convertable to an `int`. In other words, it must be within
+         * `[0, INT_MAX]`.
+         */
+        void trySetBufferSize(size_t size);
     };
 
     /**