diff --git a/src/packcc.c b/src/packcc.c
index 2a840bf..72873ae 100644
--- a/src/packcc.c
+++ b/src/packcc.c
@@ -128,7 +128,7 @@ DECLSPEC_IMPORT HRESULT WINAPI SHGetFolderPathA(HWND hwnd, int csidl, HANDLE hTo
 
 #define WEBSITE "https://github.com/arithy/packcc"
 
-#define VERSION "2.0.2"
+#define VERSION "2.0.3"
 
 #ifndef BUFFER_MIN_SIZE
 #define BUFFER_MIN_SIZE 256
@@ -3145,7 +3145,8 @@ static bool_t parse(context_t *ctx) {
             link_references(ctx, rule->expr);
         }
     }
-    mark_rules_if_used(ctx, ctx->rules.buf[0]);
+    if (ctx->rules.len > 0)
+        mark_rules_if_used(ctx, ctx->rules.buf[0]);
     {
         size_t i;
         for (i = 0; i < ctx->rules.len; i++) {
diff --git a/tests/issue_78.d/input.peg b/tests/issue_78.d/input.peg
new file mode 100644
index 0000000..60dad1a
--- /dev/null
+++ b/tests/issue_78.d/input.peg
@@ -0,0 +1 @@
+main <- ( "A"
diff --git a/tests/issue_78.d/issue_78.bats b/tests/issue_78.d/issue_78.bats
new file mode 100644
index 0000000..bb0b47a
--- /dev/null
+++ b/tests/issue_78.d/issue_78.bats
@@ -0,0 +1,9 @@
+#!/usr/bin/env bats
+
+load "$TESTDIR/utils.sh"
+
+@test "Testing issue_78.d - generation" {
+    run test_generate
+    [ "$status" -eq 10 ]
+    [[ "$output" =~ ': input.peg:1:1: Illegal rule syntax'$ ]]
+}