diff --git a/compiler/recompilation_version.m b/compiler/recompilation_version.m
index cb8bf7337..662a1d9f5 100644
--- a/compiler/recompilation_version.m
+++ b/compiler/recompilation_version.m
@@ -564,16 +564,29 @@ item_is_unchanged(nothing(A), Item2) =
 		( Item2 = nothing(A) -> yes ; no ).
 
 item_is_unchanged(Item1, Item2) = Result :-
-	% Ignore the determinism -- the modes and determinism should
-	% have been split into a separate declaration. This case
-	% can only happen if this was not a combined predicate and
-	% mode declaration. XXX We should warn about this somewhere. 
 	Item1 = pred_or_func(TVarSet1, _, ExistQVars1, PredOrFunc,
-		Name, TypesAndModes1, _Det1, Cond, Purity, Constraints1),
+		Name, TypesAndModes1, Det1, Cond, Purity, Constraints1),
 	(
 		Item2 = pred_or_func(TVarSet2, _, ExistQVars2,
-			PredOrFunc, Name, TypesAndModes2, _Det2, Cond, Purity,
+			PredOrFunc, Name, TypesAndModes2, Det2, Cond, Purity,
 			Constraints2),
+
+		% For predicates, ignore the determinism -- the modes and
+		% determinism should have been split into a separate
+		% declaration. This case can only happen if this was
+		% not a combined predicate and mode declaration
+		% (XXX We should warn about this somewhere). 
+		% For functions a determinism declaration but no modes
+		% implies the default modes. The default modes are
+		% added later by make_hlds.m, so they won't have been
+		% split into a separate declaration here.
+		(
+			PredOrFunc = function,
+			Det1 = Det2
+		;
+			PredOrFunc = predicate
+		),
+
 		pred_or_func_type_is_unchanged(TVarSet1, ExistQVars1,
 			TypesAndModes1, Constraints1, TVarSet2,
 			ExistQVars2, TypesAndModes2, Constraints2)
diff --git a/tests/recompilation/TESTS b/tests/recompilation/TESTS
index 179537aa1..0681f762c 100755
--- a/tests/recompilation/TESTS
+++ b/tests/recompilation/TESTS
@@ -9,6 +9,7 @@ TESTS_SHOULD_SUCCEED="\
 	add_instance_2_r \
 	add_type_nr \
 	change_class_r \
+	change_func_r \
 	change_instance_r \
 	change_mode_r \
 	change_type_nr \
diff --git a/tests/recompilation/change_func_r.err_exp.2 b/tests/recompilation/change_func_r.err_exp.2
new file mode 100644
index 000000000..86b2c0fd1
--- /dev/null
+++ b/tests/recompilation/change_func_r.err_exp.2
@@ -0,0 +1,2 @@
+Recompiling module `change_func_r':
+  function `change_func_r_2:changed_func/1' was modified.
diff --git a/tests/recompilation/change_func_r.exp.1 b/tests/recompilation/change_func_r.exp.1
new file mode 100644
index 000000000..d86bac9de
--- /dev/null
+++ b/tests/recompilation/change_func_r.exp.1
@@ -0,0 +1 @@
+OK
diff --git a/tests/recompilation/change_func_r.exp.2 b/tests/recompilation/change_func_r.exp.2
new file mode 100644
index 000000000..d86bac9de
--- /dev/null
+++ b/tests/recompilation/change_func_r.exp.2
@@ -0,0 +1 @@
+OK
diff --git a/tests/recompilation/change_func_r.m.1 b/tests/recompilation/change_func_r.m.1
new file mode 100644
index 000000000..41a3edbe6
--- /dev/null
+++ b/tests/recompilation/change_func_r.m.1
@@ -0,0 +1,19 @@
+:- module change_func_r.
+
+:- interface.
+
+:- import_module io.
+
+:- pred main(io__state::di, io__state::uo) is det.
+
+:- implementation.
+
+:- import_module change_func_r_2, std_util.
+
+main -->
+	( { semidet_succeed, Str = changed_func("OK\n") } ->
+		io__write_string(Str)
+	;
+		io__write_string("failed\n")
+	).
+
diff --git a/tests/recompilation/change_func_r_2.err_exp.2 b/tests/recompilation/change_func_r_2.err_exp.2
new file mode 100644
index 000000000..dadc3aaac
--- /dev/null
+++ b/tests/recompilation/change_func_r_2.err_exp.2
@@ -0,0 +1,2 @@
+Recompiling module `change_func_r_2':
+  file `change_func_r_2.m' has changed.
diff --git a/tests/recompilation/change_func_r_2.m.1 b/tests/recompilation/change_func_r_2.m.1
new file mode 100644
index 000000000..862c87cf9
--- /dev/null
+++ b/tests/recompilation/change_func_r_2.m.1
@@ -0,0 +1,9 @@
+:- module change_func_r_2.
+
+:- interface.
+
+:- func changed_func(string) = string is det.
+
+:- implementation.
+
+changed_func(X) = X.
diff --git a/tests/recompilation/change_func_r_2.m.2 b/tests/recompilation/change_func_r_2.m.2
new file mode 100644
index 000000000..a7ae8219c
--- /dev/null
+++ b/tests/recompilation/change_func_r_2.m.2
@@ -0,0 +1,12 @@
+:- module change_func_r_2.
+
+:- interface.
+
+:- func changed_func(string) = string is semidet.
+
+:- implementation.
+
+:- import_module std_util.
+
+changed_func(X) = X :-
+	semidet_succeed.