diff --git a/lib/construct.c b/lib/construct.c
index 35ba7e7..4332c8f 100644
--- a/lib/construct.c
+++ b/lib/construct.c
@@ -115,13 +115,17 @@ static void prepend_fsa(fsa_t *f, const fsa_t *o)
 	f->count = count;
 }
 
-static void construct_base(fsa_t *out, int symbol)
+static void construct_base(fsa_t *out)
 {
 	fsa_init(out);
-	const int id = fsa_add_state(out);
-	fsa_add_rule(out, id, out->initial, symbol);
-	out->initial = id;
 	out->states[0].final = true;
+	out->initial = fsa_add_state(out);
+}
+
+static void construct_symbol(fsa_t *out, int symbol)
+{
+	construct_base(out);
+	fsa_add_rule(out, out->initial, 0, symbol);
 }
 
 static void construct_star(fsa_t *out)
@@ -129,7 +133,7 @@ static void construct_star(fsa_t *out)
 	fsa_t f;
 	memcpy(&f, out, sizeof(fsa_t));
 
-	construct_base(out, EPSILON);
+	construct_symbol(out, EPSILON);
 	int f_initial, f_final;
 	add_fsa(out, &f, &f_initial, &f_final);
 	fsa_add_rule(out, out->initial, f_initial, EPSILON);
@@ -137,20 +141,46 @@ static void construct_star(fsa_t *out)
 	fsa_add_rule(out, f_final, 0, EPSILON);
 }
 
+static bool in_class(const regex_class_t *class, char c)
+{
+	for (int i = 0; i < class->count; ++i) {
+		if (class->contents[i] == c)
+			return true;
+	}
+	return false;
+}
+
+static void construct_class(fsa_t *out, const regex_class_t *class)
+{
+	construct_base(out);
+	if (class->negated) {
+		for (int i = 0; i < CHAR_COUNT; ++i) {
+			if (!in_class(class, i))
+				fsa_add_rule(out, out->initial, 0, i);
+		}
+	} else {
+		for (int i = 0; i < class->count; ++i)
+			fsa_add_rule(out, out->initial, 0, class->contents[i]);
+	}
+}
+
 static void construct_term(const regex_term_t *term, fsa_t *out)
 {
 	switch (term->type) {
 	case REGEX_TERM_EMPTY:
-		construct_base(out, EPSILON);
+		construct_symbol(out, EPSILON);
 		break;
 	case REGEX_TERM_LITERAL:
-		construct_base(out, term->literal);
+		construct_symbol(out, term->literal);
 		break;
 	case REGEX_TERM_SUBEXPR:
 		construct_nfa(&term->subexpr, out);
 		break;
-	case REGEX_TERM_WILDCARD:
 	case REGEX_TERM_CLASS:
+		construct_class(out, &term->class);
+		break;
+
+	case REGEX_TERM_WILDCARD:
 		assert(false);
 		break;
 	}
diff --git a/tests/construct_tests.c b/tests/construct_tests.c
index eb398cf..20f7f87 100644
--- a/tests/construct_tests.c
+++ b/tests/construct_tests.c
@@ -186,6 +186,71 @@ static void test_subexpression(void)
 	fsa_free(&fsa);
 }
 
+static void test_class(void)
+{
+	char *class_contents = malloc(3);
+	class_contents[0] = 'a';
+	class_contents[1] = 'b';
+	class_contents[2] = 'c';
+	regex_term_t *terms = malloc(1 * sizeof(regex_term_t));
+	terms[0].quantifier = REGEX_QUANTIFIER_NONE;
+	terms[0].type = REGEX_TERM_CLASS;
+	terms[0].class.negated = false;
+	terms[0].class.count = terms[0].class.capacity = 3;
+	terms[0].class.contents = class_contents;
+	regex_sequence_t *alternatives = malloc(1 * sizeof(regex_sequence_t));
+	alternatives[0].count = alternatives[0].capacity = 1;
+	alternatives[0].contents = terms;
+	const regex_t regex
+	    = { .count = 1, .capacity = 1, .contents = alternatives };
+
+	fsa_t fsa;
+	construct_nfa(&regex, &fsa);
+
+	ASSERT_TRUE(accepts(&fsa, "a"));
+	ASSERT_TRUE(accepts(&fsa, "b"));
+	ASSERT_TRUE(accepts(&fsa, "c"));
+	ASSERT_FALSE(accepts(&fsa, ""));
+	ASSERT_FALSE(accepts(&fsa, "aa"));
+	ASSERT_FALSE(accepts(&fsa, "d"));
+
+	regex_free(&regex);
+	fsa_free(&fsa);
+}
+
+static void test_negated_class(void)
+{
+	char *class_contents = malloc(3);
+	class_contents[0] = 'a';
+	class_contents[1] = 'b';
+	class_contents[2] = 'c';
+	regex_term_t *terms = malloc(1 * sizeof(regex_term_t));
+	terms[0].quantifier = REGEX_QUANTIFIER_NONE;
+	terms[0].type = REGEX_TERM_CLASS;
+	terms[0].class.negated = true;
+	terms[0].class.count = terms[0].class.capacity = 3;
+	terms[0].class.contents = class_contents;
+	regex_sequence_t *alternatives = malloc(1 * sizeof(regex_sequence_t));
+	alternatives[0].count = alternatives[0].capacity = 1;
+	alternatives[0].contents = terms;
+	const regex_t regex
+	    = { .count = 1, .capacity = 1, .contents = alternatives };
+
+	fsa_t fsa;
+	construct_nfa(&regex, &fsa);
+
+	ASSERT_TRUE(accepts(&fsa, "d"));
+	ASSERT_TRUE(accepts(&fsa, "e"));
+	ASSERT_FALSE(accepts(&fsa, "a"));
+	ASSERT_FALSE(accepts(&fsa, "b"));
+	ASSERT_FALSE(accepts(&fsa, "c"));
+	ASSERT_FALSE(accepts(&fsa, ""));
+	ASSERT_FALSE(accepts(&fsa, "aa"));
+
+	regex_free(&regex);
+	fsa_free(&fsa);
+}
+
 static void test_sequence_containing_starred_union(void)
 {
 	// ab(c|d)*
@@ -325,6 +390,8 @@ int main(void)
 	test_union();
 	test_star();
 	test_subexpression();
+	test_class();
+	test_negated_class();
 
 	// Compound expressions
 	test_sequence_containing_starred_union();