diff --git a/src/asm/asmy.y b/src/asm/asmy.y
index ffeb7182..d5816b5d 100644
--- a/src/asm/asmy.y
+++ b/src/asm/asmy.y
@@ -540,7 +540,7 @@ macro : T_ID {
 		yy_set_state(LEX_STATE_NORMAL);
 
 		if (!fstk_RunMacro($1)) {
-			yyerror("Macro '%s' not defined", $1);
+			fatalerror("Macro '%s' not defined", $1);
 		}
 	};
 
diff --git a/src/asm/fstack.c b/src/asm/fstack.c
index 5cc5fd00..6b38d8c7 100644
--- a/src/asm/fstack.c
+++ b/src/asm/fstack.c
@@ -255,6 +255,8 @@ fstk_RunMacro(char *s)
 		sym_UseNewMacroArgs();
 		nCurrentStatus = STAT_isMacro;
 		strcpy(tzCurrentFileName, s);
+		if (sym->pMacro == NULL)
+			return 0;
 		pCurrentMacro = sym;
 		CurrentFlexHandle =
 		    yy_scan_bytes(pCurrentMacro->pMacro,