diff --git a/NEWS b/NEWS
index 0c20a3125..474d2082e 100644
--- a/NEWS
+++ b/NEWS
@@ -1,6 +1,7 @@
 New in spot 1.99.5a (not yet released)
 
-  Nothing yet.
+  Bug fixes:
+  * automaton parser was ignoring the "unambiguous" property.
 
 New in spot 1.99.5 (2015-11-03)
 
diff --git a/src/parseaut/parseaut.yy b/src/parseaut/parseaut.yy
index 3f824db4a..fd5c3b0f5 100644
--- a/src/parseaut/parseaut.yy
+++ b/src/parseaut/parseaut.yy
@@ -436,6 +436,8 @@ header: format-version header-items
 	      res.h->aut->prop_stutter_sensitive(ss);
 	      bool iw = res.props.find("inherently-weak") != e;
 	      res.h->aut->prop_inherently_weak(iw);
+	      bool iu = res.props.find("unambiguous") != e;
+	      res.h->aut->prop_unambiguous(iu);
 	    }
 	}
 
diff --git a/src/tests/unambig.test b/src/tests/unambig.test
index 24a826470..ed01baf58 100755
--- a/src/tests/unambig.test
+++ b/src/tests/unambig.test
@@ -170,5 +170,53 @@ State: 0
 State: 1
 State: 2
 --END--
+HOA: v1
+AP: 0
+States: 3
+Start: 0
+Acceptance: 1 Inf(0)
+properties: explicit-labels state-acc trans-labels unambiguous
+--BODY--
+State: 0
+[t] 2
+[t] 1
+State: 1
+State: 2
+--END--
 EOF
-run 0 $autfilt -q --is-unambiguous input
+
+# Make sure we preserve the "unambiguous" property if it is given.
+run 0 $autfilt -H --is-unambiguous input >output
+
+cat >expected <<EOF
+HOA: v1
+name: ""
+States: 3
+Start: 0
+AP: 0
+acc-name: Buchi
+Acceptance: 1 Inf(0)
+properties: trans-labels explicit-labels state-acc
+--BODY--
+State: 0
+[t] 2
+[t] 1
+State: 1
+State: 2
+--END--
+HOA: v1
+States: 3
+Start: 0
+AP: 0
+acc-name: Buchi
+Acceptance: 1 Inf(0)
+properties: trans-labels explicit-labels state-acc unambiguous
+--BODY--
+State: 0
+[t] 2
+[t] 1
+State: 1
+State: 2
+--END--
+EOF
+diff output expected