diff --git a/osc-time.lisp b/osc-time.lisp
index f334daf..ae75b24 100644
--- a/osc-time.lisp
+++ b/osc-time.lisp
@@ -22,9 +22,10 @@
   "Returns a fixed-point 64 bit NTP-style timetag, where the top 32
 bits represent seconds since midnight 19000101, and the bottom 32 bits
 represent the fractional parts of a second."
-  (multiple-value-bind (secs usecs)
-      (sb-ext:get-time-of-day)
-    (the timetag (unix-secs+usecs->timetag secs usecs))))
+  #+sbcl (multiple-value-bind (secs usecs)
+             (sb-ext:get-time-of-day)
+           (the timetag (unix-secs+usecs->timetag secs usecs)))
+  #-sbcl (error "Can't encode timetags using this implementation."))
 
 (defun timetag+ (original seconds-offset)
   (declare (type timetag original))
@@ -39,9 +40,10 @@ represent the fractional parts of a second."
 (defun get-unix-time ()
   "Returns a a double-float representing real-time now in seconds,
 with microsecond precision, relative to 19700101."
-  (multiple-value-bind (secs usecs)
-      (sb-ext:get-time-of-day)
-    (the double-float (+ secs (microseconds->subsecs usecs)))))
+  #+sbcl (multiple-value-bind (secs usecs)
+             (sb-ext:get-time-of-day)
+           (the double-float (+ secs (microseconds->subsecs usecs))))
+  #-sbcl (error "Can't encode timetags using this implementation."))
 
 (defun unix-time->timetag (unix-time)
   (multiple-value-bind (secs subsecs)
diff --git a/osc.lisp b/osc.lisp
index 3a9e82a..7034b46 100644
--- a/osc.lisp
+++ b/osc.lisp
@@ -341,7 +341,7 @@ with the current time use (encode-timetag :time)."
   #+openmcl (encode-int32 (CCL::SINGLE-FLOAT-BITS f))
   #+allegro (encode-int32 (multiple-value-bind (x y) (excl:single-float-to-shorts f)
                             (+ (ash x 16) y)))
-  #-(or sbcl cmucl openmcl allegro) (error "cant encode floats using this implementation"))
+  #-(or sbcl cmucl openmcl allegro) (error "Can't encode floats using this implementation."))
 
 (defun decode-float32 (s)
   "ieee754 float from a vector of 4 bytes in network byte order"
@@ -350,7 +350,7 @@ with the current time use (encode-timetag :time)."
   #+openmcl (CCL::HOST-SINGLE-FLOAT-FROM-UNSIGNED-BYTE-32 (decode-uint32 s))
   #+allegro (excl:shorts-to-single-float (ldb (byte 16 16) (decode-int32 s))
                                          (ldb (byte 16 0) (decode-int32 s)))
-  #-(or sbcl cmucl openmcl allegro) (error "cant decode floats using this implementation"))
+  #-(or sbcl cmucl openmcl allegro) (error "Can't decode floats using this implementation."))
 
 (defmacro defint-decoder (num-of-octets &optional docstring)
   (let ((decoder-name (intern (format nil "~:@(decode-uint~)~D" (* 8 num-of-octets))))