diff --git a/Tools/Breakasm/asm.cpp b/Tools/Breakasm/asm.cpp
index 3f98cf7..347d6b0 100644
--- a/Tools/Breakasm/asm.cpp
+++ b/Tools/Breakasm/asm.cpp
@@ -504,9 +504,21 @@ static void parse_line (char **text, line& ln)
 
 // ****************************************************************
 
+int emit_mode = 1;		// 1: output byte stream; 0: just change origin
+
+void set_emit_mode(int mode)
+{
+	emit_mode = mode;
+}
+
 void emit (uint8_t b)
 {
-	PRG[org++] = b;
+	if (emit_mode) {
+		PRG[org++] = b;
+	}
+	else {
+		org++;
+	}
 }
 
 static oplink optab[] = {
@@ -577,9 +589,58 @@ static void cleanup (void)
 	}
 }
 
-int assemble (char *text, char* source_name, uint8_t *prg)
+static void assemble_text(char* text)
 {
+	oplink* opl;
 	line l;
+	int listing = 0;
+
+	while (1) {
+		if (*text == 0) break;
+		parse_line(&text, l);
+
+		// Add label
+		if (strlen(l.label) > 1) {
+			add_label(l.label, org);
+		}
+
+		long org_before = org;
+
+		// Execute command
+		if (strlen(l.cmd) > 1) {
+			opl = optab;
+			while (1) {
+				if (opl->name == NULL) {
+					printf("ERROR(%s,%i): Unknown command %s\n", get_source_name().c_str(), get_linenum(), l.cmd);
+					break;
+				}
+				else if (!_stricmp(opl->name, l.cmd)) {
+					_strupr(l.cmd);
+					opl->handler(l.cmd, l.op);
+					break;
+				}
+				opl++;
+			}
+			if (stop) break;
+		}
+
+		// Listing
+		if (listing) {
+			printf("0x%08X: ", org_before);
+			int num_bytes = org - org_before;
+			for (int i = 0; i < num_bytes; i++) {
+				printf("%02X ", PRG[org_before + i]);
+			}
+			printf("%s: \'%s\' \'%s\'\n", l.label, l.cmd, l.op);
+			printf("\n");
+		}
+
+		nextline();
+	}
+}
+
+int assemble (char *text, char* source_name, uint8_t *prg)
+{
 	oplink *opl;
 	PRG = prg;
 	org = 0;
@@ -603,36 +664,7 @@ int assemble (char *text, char* source_name, uint8_t *prg)
 	}
 	nextline();
 
-	while (1) {
-		if (*text == 0) break;
-		parse_line (&text, l);
-
-		//printf ( "%s: \'%s\' \'%s\'\n", l.label, l.cmd, l.op );
-
-		// Add label
-		if ( strlen (l.label) > 1 ) {
-			add_label ( l.label, org );
-		}
-
-		// Execute command
-		if ( strlen (l.cmd) > 1 ) {
-			opl = optab;
-			while (1) {
-				if ( opl->name == NULL ) {
-					printf ("ERROR(%s,%i): Unknown command %s\n", get_source_name().c_str(), get_linenum(), l.cmd);
-					break;
-				}
-				else if ( !_stricmp (opl->name, l.cmd) ) {
-					_strupr (l.cmd);
-					opl->handler (l.cmd, l.op);
-					break;
-				}
-				opl++;
-			}
-			if (stop) break;
-		}
-		nextline();
-	}
+	assemble_text(text);
 
 	// Patch jump/branch offsets.
 	do_expr_labels();
@@ -656,42 +688,10 @@ int assemble (char *text, char* source_name, uint8_t *prg)
 /// <param name="source_name">Source file name</param>
 void assemble_include(char* text, char* source_name)
 {
-	line l;
-	oplink* opl;
-
 	source_name_stack.push_back(source_name);
 	linenum_stack.push_back(1);
 
-	while (1) {
-		if (*text == 0) break;
-		parse_line(&text, l);
-
-		//printf ( "%s: \'%s\' \'%s\'\n", l.label, l.cmd, l.op );
-
-		// Add label
-		if (strlen(l.label) > 1) {
-			add_label(l.label, org);
-		}
-
-		// Execute command
-		if (strlen(l.cmd) > 1) {
-			opl = optab;
-			while (1) {
-				if (opl->name == NULL) {
-					printf("ERROR(%s,%i): Unknown command %s\n", get_source_name().c_str(), get_linenum(), l.cmd);
-					break;
-				}
-				else if (!_stricmp(opl->name, l.cmd)) {
-					_strupr(l.cmd);
-					opl->handler(l.cmd, l.op);
-					break;
-				}
-				opl++;
-			}
-			if (stop) break;
-		}
-		nextline();
-	}
+	assemble_text(text);
 
 	source_name_stack.pop_back();
 	linenum_stack.pop_back();
diff --git a/Tools/Breakasm/asmexpr.cpp b/Tools/Breakasm/asmexpr.cpp
index ad1b9a8..7f797ed 100644
--- a/Tools/Breakasm/asmexpr.cpp
+++ b/Tools/Breakasm/asmexpr.cpp
@@ -359,7 +359,7 @@ static node_t* addnode(std::list<node_t*>& tree, token_t* token, int depth)
 }
 
 // executing the tree (semantic analysis)
-static node_t * evaluate (std::list<node_t*>& tree, node_t * expr, long *lvalue, bool quiet)
+static node_t * evaluate (std::list<node_t*>& tree, node_t * expr, long *lvalue, bool quiet, bool& syntax_error)
 {
 	node_t * curr;
 	long rvalue = 0, mvalue;
@@ -379,6 +379,7 @@ static node_t * evaluate (std::list<node_t*>& tree, node_t * expr, long *lvalue,
 		token = curr->token;
 		if ( token->type == TOKEN_OP && isunary(token->op) ) {
 			if (curr->rvalue == NULL) {
+				syntax_error = true;
 				if (!quiet) {
 					printf("Missing identifier\n");
 					errors++;
@@ -401,7 +402,7 @@ static node_t * evaluate (std::list<node_t*>& tree, node_t * expr, long *lvalue,
 
 			if ( curr->depth > expr->depth ) {  // nested expression
 				if (debug) printf ( "SUBEVAL " );
-				curr = evaluate (tree, curr, &mvalue, quiet);
+				curr = evaluate (tree, curr, &mvalue, quiet, syntax_error);
 				//printf ( "SUB LVALUE : %i\n", mvalue.num.value );
 			}
 			else if ( token->type == TOKEN_IDENT) {
@@ -413,10 +414,11 @@ static node_t * evaluate (std::list<node_t*>& tree, node_t * expr, long *lvalue,
 				}
 				else {
 					label_s* label = label_lookup(token->string);
-					if (label) {
+					if (label && label->orig != UNDEF && !label->composite) {
 						mvalue = label->orig;
 					}
 					else {
+						syntax_error = true;
 						if (!quiet) {
 							printf("Undefined identifier: %s", token->string);
 							errors++;
@@ -468,6 +470,7 @@ static node_t * evaluate (std::list<node_t*>& tree, node_t * expr, long *lvalue,
 			else rvalue = mvalue;
 		}
 		else {
+			syntax_error = true;
 			if (!quiet) {
 				printf("Identifier required\n");
 				errors++;
@@ -583,7 +586,13 @@ long eval_expr(char* text, bool debug, bool quiet)
 	// Execute the tree
 
 	long result = 0;
-	evaluate(tree.nodes, root->rvalue->rvalue, &result, quiet);
+	bool syntax_error = false;
+	if (root) {
+		evaluate(tree.nodes, root->rvalue->rvalue, &result, quiet, syntax_error);
+	}
+	if (syntax_error) {
+		result = 0;
+	}
 
 	if (debug)
 		printf("Source expression: %s, result: %d (0x%08X)\n", text, result, result);