diff --git a/pasp-mode.el b/pasp-mode.el
index 7f83645..5daf08e 100644
--- a/pasp-mode.el
+++ b/pasp-mode.el
@@ -199,9 +199,12 @@
 Argument ENCODING The current buffer which holds the problem encoding.
 Optional argument INSTANCE The problem instance which is solved by the encoding.
   If no instance it is assumed to be also in the encoding file."
-  (if 'instance
-      (concat pasp-clingo-path " " pasp-clingo-options " " encoding " " instance)
-    (concat pasp-clingo-path " " pasp-clingo-options " " encoding)))
+  (if instance
+      (concat pasp-clingo-path " " pasp-clingo-options " "
+              (shell-quote-argument encoding) " "
+              (shell-quote-argument instance))
+    (concat pasp-clingo-path " " pasp-clingo-options " "
+            (shell-quote-argument encoding))))
 
 (defun pasp-run-clingo (encoding &optional instance)
   "Run Clingo with some ASP input files.
it' value='switch'/></form></td></tr>
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<div class='path'>path: <a href='/guix/log/?id=573d478f729d732b65b2dabc295a31e08f9ad32b'>root</a>/<a href='/guix/log/build-aux?id=573d478f729d732b65b2dabc295a31e08f9ad32b'>build-aux</a>/<a href='/guix/log/build-aux/check-final-inputs-self-contained.scm?id=573d478f729d732b65b2dabc295a31e08f9ad32b'>check-final-inputs-self-contained.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/build-aux/check-final-inputs-self-contained.scm?id=573d478f729d732b65b2dabc295a31e08f9ad32b&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2021-03-10 19:41:15 +0100'>2021-03-10</span></td><td><a href='/guix/commit/build-aux/check-final-inputs-self-contained.scm?id=33bb89c939aee88bd211964db600df65d1b656af'>ci: Remove hydra support.</a><span class='msg-avail'>...</span></td><td>Mathieu Othacehe</td></tr>
<tr><td><span title='2018-12-04 10:57:56 +0100'>2018-12-04</span></td><td><a href='/guix/commit/build-aux/check-final-inputs-self-contained.scm?id=0bc02becca1b4b0b3eddb7972567a75f0d464b72'>Remove most references to hydra.gnu.org.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2018-03-25 00:26:13 +0100'>2018-03-25</span></td><td><a href='/guix/commit/build-aux/check-final-inputs-self-contained.scm?id=4debffadb7e166e34fb2ef00e75c4b73977ede15'>maint: Adjust 'check-final-inputs-self-contained' for glibc:static.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2017-05-08 16:29:23 +0200'>2017-05-08</span></td><td><a href='/guix/commit/build-aux/check-final-inputs-self-contained.scm?id=c8ba269c26c85c5eae6bf5be9add881111c18a22'>maint: Use 'G_' in build-aux/ scripts.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>
<tr><td><span title='2016-12-18 12:37:26 +0100'>2016-12-18</span></td><td><a href='/guix/commit/build-aux/check-final-inputs-self-contained.scm?id=8a4c98889270c163581231692fef64d9433b101f'>build: check-final-inputs-self-contained has an exception for 'bash:include'.</a><span class='msg-avail'>...</span></td><td>Ludovic Courtès</td></tr>