diff --git a/lib/fsa.c b/lib/fsa.c
index a4611aa..9d73a88 100644
--- a/lib/fsa.c
+++ b/lib/fsa.c
@@ -47,11 +47,10 @@ int fsa_add_state(fsa_t *fsa)
 	return fsa->count++;
 }
 
-void fsa_add_rule(fsa_t *fsa, int from, int to, int input)
+void fsa_add_rule(fsa_t *fsa, int from, int to, char input)
 {
 	assert(fsa->count > from);
 	assert(fsa->count > to);
-	assert(input < ALPHABET_SIZE);
 
 	fsa_state_t *state = &fsa->states[from];
 	if (state->count >= state->capacity) {
diff --git a/lib/include/fsa.h b/lib/include/fsa.h
index 85ee342..7eb474e 100644
--- a/lib/include/fsa.h
+++ b/lib/include/fsa.h
@@ -8,14 +8,9 @@
 
 #include <stdbool.h>
 
-#define CHAR_COUNT 256
-#define ALPHABET_SIZE (CHAR_COUNT + 1)
-
-// Use one more than any valid char to represent empty string
-#define EPSILON CHAR_COUNT
-
 typedef struct {
-	int input, next;
+	int next;
+	char input;
 } fsa_rule_t;
 
 typedef struct {
@@ -33,6 +28,6 @@ void fsa_init(fsa_t *fsa);
 void fsa_free(const fsa_t *fsa);
 
 int fsa_add_state(fsa_t *fsa);
-void fsa_add_rule(fsa_t *fsa, int from, int to, int input);
+void fsa_add_rule(fsa_t *fsa, int from, int to, char input);
 
 #endif