diff --git a/src/zscript/ast.cpp b/src/zscript/ast.cpp
index 5757e4b041..d4a98691e0 100644
--- a/src/zscript/ast.cpp
+++ b/src/zscript/ast.cpp
@@ -141,7 +141,7 @@ static void PrintEnum(FString &out, ZCC_TreeNode *node)
 static void PrintEnumNode(FString &out, ZCC_TreeNode *node)
 {
 	ZCC_EnumNode *enode = (ZCC_EnumNode *)node;
-	out.AppendFormat("(enum-node '%s' ", FName(enode->ElemName));
+	out.AppendFormat("(enum-node '%s' ", FName(enode->ElemName).GetChars());
 	PrintNodes(out, enode->ElemValue, ')');
 }
 
diff --git a/src/zscript/zcc-parse.lemon b/src/zscript/zcc-parse.lemon
index 8f029b83f1..ba2776d4bd 100644
--- a/src/zscript/zcc-parse.lemon
+++ b/src/zscript/zcc-parse.lemon
@@ -69,14 +69,16 @@
 %type opt_func_body {ZCC_CompoundStmt *}
 %type function_body {ZCC_CompoundStmt *}
 
-main ::= translation_unit. { stat->sc.ScriptMessage("Parse complete\n"); }
+main ::= translation_unit(A). { stat->TopNode = A; stat->sc.ScriptMessage("Parse complete\n"); }
 
-translation_unit ::= .
-translation_unit ::= translation_unit external_declaration.
-translation_unit ::= translation_unit EOF.
-translation_unit ::= error.
+%type translation_unit {ZCC_TreeNode *}
+translation_unit(X) ::= .												{ X = NULL; }
+translation_unit(X) ::= translation_unit(A) external_declaration(B).	{ SAFE_APPEND(A,B); X = A; }
+translation_unit(X) ::= translation_unit(A) EOF.						{ X = A; }
+translation_unit(X) ::= error.											{ X = NULL; }
 
-external_declaration ::= class_definition.
+%type external_declaration {ZCC_TreeNode *}
+external_declaration(X) ::= class_definition(A).						{ X = A; }
 
 /* Optional bits. */
 opt_semicolon ::= .
@@ -317,7 +319,6 @@ state_line(X) ::= NWS(A) NWS(B) expr state_opts(C) state_action(D).
 {
 	NEW_AST_NODE(StateLine, line);
 	const char *sprite = FName(A.Name()).GetChars();
-	memset(line, 0, sizeof(*line));
 	if (strlen(sprite) != 4)
 	{
 		Printf("Sprite name '%s' must be four characters", sprite);
@@ -650,7 +651,7 @@ func_params(X) ::= VOID.					{ X = NULL; }
 func_params(X) ::= func_param_list(A).		{ X = A; }
 
 func_param_list(X) ::= func_param(A).		{ X = A; }
-func_param_list(X) ::= func_param(A) COMMA func_param_list(B).	{ X = A; A->AppendSibling(B); }
+func_param_list(X) ::= func_param_list(A) COMMA func_param(B).	{ X = A; A->AppendSibling(B); }
 
 func_param(X) ::= func_param_flags(A) type(B) IDENTIFIER(C).
 {
@@ -1194,7 +1195,8 @@ iteration_statement(X) ::= FOR LPAREN for_init(IN) SEMICOLON opt_expr(EX) SEMICO
 	iter->LoopBumper = DO;
 	iter->CheckAt = ZCC_IterationStmt::Start;
 	// The initialization expression appears outside the loop
-	IN->AppendSibling(iter);
+	// for_init may be NULL if there is no initialization.
+	SAFE_APPEND(IN, iter);
 	// And the whole thing gets wrapped inside a compound statement in case the loop
 	// initializer defined any variables.
 	NEW_AST_NODE(CompoundStmt, wrap);
diff --git a/src/zscript/zcc_parser.cpp b/src/zscript/zcc_parser.cpp
index 69e501d100..32816ec0c8 100644
--- a/src/zscript/zcc_parser.cpp
+++ b/src/zscript/zcc_parser.cpp
@@ -229,6 +229,15 @@ static void DoParse(const char *filename)
 		fclose(f);
 	}
 #endif
+	FString ast = ZCC_PrintAST(state.TopNode);
+	FString astfile = ExtractFileBase(filename, false);
+	astfile << ".ast";
+	f = fopen(astfile, "w");
+	if (f != NULL)
+	{
+		fputs(ast.GetChars(), f);
+		fclose(f);
+	}
 }
 
 CCMD(parse)
diff --git a/src/zscript/zcc_parser.h b/src/zscript/zcc_parser.h
index 5256e46371..d0d4e3b638 100644
--- a/src/zscript/zcc_parser.h
+++ b/src/zscript/zcc_parser.h
@@ -7,6 +7,7 @@ struct ZCCParseState
 	FScanner &sc;
 	FSharedStringArena Strings;
 	FMemArena SyntaxArena;
+	struct ZCC_TreeNode *TopNode;
 };
 
 union ZCCToken
@@ -206,7 +207,7 @@ struct ZCC_TreeNode
 		}
 
 		// The new sibling node should only be in a list with itself.
-		assert(sibling->SiblingNext == sibling && sibling->SiblingNext == sibling);
+		assert(sibling->SiblingNext == sibling && sibling->SiblingPrev == sibling);
 
 		// Check integrity of our sibling list.
 		assert(SiblingPrev->SiblingNext == this);