diff --git a/src/pre.l b/src/pre.l
index ebc6cf8c032..8d2b5f70b3a 100644
--- a/src/pre.l
+++ b/src/pre.l
@@ -2299,7 +2299,7 @@ CHARLIT   (("'"\\[0-7]{1,3}"'")|("'"\\."'")|("'"[^'\\\n]{1,4}"'"))
   					}
 <DefName>{ID}{B}+"1"/[ \r\t\n]		{ // special case: define with 1 -> can be "guard"
   					  //printf("Define `%s'\n",yytext);
-  					  g_argDict = 0;
+					  delete g_argDict; g_argDict=0;
 					  g_defArgs = -1;
                                           g_defArgsStr.resize(0);
 					  g_defName = yytext;
@@ -2328,7 +2328,7 @@ CHARLIT   (("'"\\[0-7]{1,3}"'")|("'"\\."'")|("'"[^'\\\n]{1,4}"'"))
 					  g_expectGuard=FALSE;
   					}
 <DefName>{ID}/{B}*"\n"			{ // empty define
-  					  g_argDict = 0;
+					  delete g_argDict; g_argDict=0;
 					  g_defArgs = -1;
 					  g_defName = yytext;
                                           g_defArgsStr.resize(0);
@@ -2357,7 +2357,7 @@ CHARLIT   (("'"\\[0-7]{1,3}"'")|("'"\\."'")|("'"[^'\\\n]{1,4}"'"))
   					}
 <DefName>{ID}/{B}*			{ // define with content
   					  //printf("Define `%s'\n",yytext);
-  					  g_argDict = 0;
+					  delete g_argDict; g_argDict=0;
 					  g_defArgs = -1;
                                           g_defArgsStr.resize(0);
 					  g_defText.resize(0);