diff --git a/lisp/erc/erc.el b/lisp/erc/erc.el
index 88c105040c5..0da837012cc 100644
--- a/lisp/erc/erc.el
+++ b/lisp/erc/erc.el
@@ -2817,20 +2817,17 @@ present."
   (let ((prop-val (erc-get-parsed-vector position)))
     (and prop-val (member (erc-response.command prop-val) list))))
 
-(defvar-local erc-send-input-line-function 'erc-send-input-line)
+(defvar-local erc-send-input-line-function 'erc-send-input-line
+  "Function for sending lines lacking a leading user command.
+When a line typed into a buffer contains an explicit command, like /msg,
+a corresponding handler (here, erc-cmd-MSG) is called.  But lines typed
+into a channel or query buffer already have an implicit target and
+command (PRIVMSG).  This function is called on such occasions and also
+for special purposes (see erc-dcc.el).")
 
 (defun erc-send-input-line (target line &optional force)
-  "Send LINE to TARGET.
-
-See also `erc-server-send'."
-  (setq line (format "PRIVMSG %s :%s"
-                     target
-                     ;; If the line is empty, we still want to
-                     ;; send it - i.e. an empty pasted line.
-                     (if (string= line "\n")
-                         " \n"
-                       line)))
-  (erc-server-send line force target))
+  "Send LINE to TARGET."
+  (erc-message "PRIVMSG" (concat target " " line) force))
 
 (defun erc-get-arglist (fun)
   "Return the argument list of a function without the parens."
diff --git a/test/lisp/erc/erc-tests.el b/test/lisp/erc/erc-tests.el
index 6ed26f68289..685f4e2bea2 100644
--- a/test/lisp/erc/erc-tests.el
+++ b/test/lisp/erc/erc-tests.el
@@ -228,4 +228,66 @@
     (kill-buffer "*erc-protocol*")
     (should-not erc-debug-irc-protocol)))
 
+
+;; The point of this test is to ensure output is handled identically
+;; regardless of whether a command handler is summoned.
+
+(ert-deftest erc-process-input-line ()
+  (let (erc-server-last-sent-time
+        erc-server-flood-queue
+        (orig-erc-cmd-MSG (symbol-function 'erc-cmd-MSG))
+        calls)
+    (with-temp-buffer
+      (cl-letf (((symbol-function 'erc-cmd-MSG)
+                 (lambda (line)
+                   (push line calls)
+                   (funcall orig-erc-cmd-MSG line)))
+                ((symbol-function 'erc-server-buffer)
+                 (lambda () (current-buffer)))
+                ((symbol-function 'erc-server-process-alive)
+                 (lambda () t))
+                ((symbol-function 'erc-server-send-queue)
+                 #'ignore)
+                ((symbol-function 'erc-default-target)
+                 (lambda () "" "#chan")))
+
+        (ert-info ("Dispatch to user command handler")
+
+          (ert-info ("Baseline")
+            (erc-process-input-line "/msg #chan hi\n")
+            (should (equal (pop calls) " #chan hi"))
+            (should (equal (pop erc-server-flood-queue)
+                           '("PRIVMSG #chan :hi\r\n" . utf-8))))
+
+          (ert-info ("Spaces preserved")
+            (erc-process-input-line "/msg #chan hi you\n")
+            (should (equal (pop calls) " #chan hi you"))
+            (should (equal (pop erc-server-flood-queue)
+                           '("PRIVMSG #chan :hi you\r\n" . utf-8))))
+
+          (ert-info ("Empty line honored")
+            (erc-process-input-line "/msg #chan\n")
+            (should (equal (pop calls) " #chan"))
+            (should (equal (pop erc-server-flood-queue)
+                           '("PRIVMSG #chan :\r\n" . utf-8)))))
+
+        (ert-info ("Implicit cmd via `erc-send-input-line-function'")
+
+          (ert-info ("Baseline")
+            (erc-process-input-line "hi")
+            (should (equal (pop erc-server-flood-queue)
+                           '("PRIVMSG #chan :hi\r\n" . utf-8))))
+
+          (ert-info ("Spaces preserved")
+            (erc-process-input-line "hi you")
+            (should (equal (pop erc-server-flood-queue)
+                           '("PRIVMSG #chan :hi you\r\n" . utf-8))))
+
+          (ert-info ("Empty line transmitted without injected-space kludge")
+            (erc-process-input-line "")
+            (should (equal (pop erc-server-flood-queue)
+                           '("PRIVMSG #chan :\r\n" . utf-8))))
+
+          (should-not calls))))))
+
 ;;; erc-tests.el ends here