diff --git a/MathEval/parser.cpp b/MathEval/parser.cpp
index 97048d87553f71e936e60ce33d17cd85b63c175b..8944f5f000654e4afd0712674576906cd4526aa0 100644
--- a/MathEval/parser.cpp
+++ b/MathEval/parser.cpp
@@ -54,7 +54,14 @@ int yyerror (char *s);
    is generated by scanner generator).  */
 int yylex (void);
 
-#line 41 "parser.y"
+/* Function used to flush the internal flex buffer when we exit
+   prematurely (i.e., in case of a parse error) so that the next time
+   we call the scanner, all is nicely reset. Without this, the
+   behaviour of the next call after an error is unpredictable.  */
+int force_buffer_flush(void);
+
+
+#line 48 "parser.y"
 #ifndef YYSTYPE
 typedef union {
   Node *node;
@@ -128,8 +135,8 @@ static const short yyrhs[] =
 /* YYRLINE[YYN] -- source line where rule number YYN was defined. */
 static const short yyrline[] =
 {
-       0,    64,    72,    75,    78,    82,    86,    90,    94,    98,
-     102,   106
+       0,    71,    78,    81,    84,    88,    92,    96,   100,   104,
+     108,   112
 };
 #endif
 
@@ -915,76 +922,75 @@ yyreduce:
   switch (yyn) {
 
 case 1:
-#line 64 "parser.y"
+#line 71 "parser.y"
 {
   matheval_root = yyvsp[-1].node;
-  yyerrok;
   return 1;
 ;
     break;}
 case 2:
-#line 72 "parser.y"
+#line 78 "parser.y"
 {
   yyval.node = yyvsp[0].node;
 ;
     break;}
 case 3:
-#line 75 "parser.y"
+#line 81 "parser.y"
 {
   yyval.node = yyvsp[0].node;
 ;
     break;}
 case 4:
-#line 78 "parser.y"
+#line 84 "parser.y"
 {
   /* Create addition binary operator node.  */
   yyval.node = node_create ('b', '+', yyvsp[-2].node, yyvsp[0].node);
 ;
     break;}
 case 5:
-#line 82 "parser.y"
+#line 88 "parser.y"
 {
   /* Create subtraction binary operator node.  */
   yyval.node = node_create ('b', '-', yyvsp[-2].node, yyvsp[0].node);
 ;
     break;}
 case 6:
-#line 86 "parser.y"
+#line 92 "parser.y"
 {
   /* Create multiplication binary operator node.  */
   yyval.node = node_create ('b', '*', yyvsp[-2].node, yyvsp[0].node);
 ;
     break;}
 case 7:
-#line 90 "parser.y"
+#line 96 "parser.y"
 {
   /* Create division binary operator node.  */
   yyval.node = node_create ('b', '/', yyvsp[-2].node, yyvsp[0].node);
 ;
     break;}
 case 8:
-#line 94 "parser.y"
+#line 100 "parser.y"
 {
   /* Create minus unary operator node.  */
   yyval.node = node_create ('u', '-', yyvsp[0].node);
 ;
     break;}
 case 9:
-#line 98 "parser.y"
+#line 104 "parser.y"
 {
   /* Create exponentiation unary operator node.  */
   yyval.node = node_create ('b', '^', yyvsp[-2].node, yyvsp[0].node);
 ;
     break;}
 case 10:
-#line 102 "parser.y"
+#line 108 "parser.y"
 {
   /* Create function node.  */
   yyval.node = node_create ('f', yyvsp[-3].record, yyvsp[-1].node);
 ;
     break;}
 case 11:
-#line 106 "parser.y"
+#line 112 "parser.y"
 {
   yyval.node = yyvsp[-1].node;
 ;
@@ -1222,7 +1228,7 @@ yyreturn:
 #endif
   return yyresult;
 }
-#line 111 "parser.y"
+#line 117 "parser.y"
 
 
 int yyerror(char* s)
@@ -1230,5 +1236,6 @@ int yyerror(char* s)
   /* Indicate parsing error through appropriate flag and stop
      parsing.  */
   matheval_ok = 0;
+  force_buffer_flush();
   return 0;
 }
diff --git a/MathEval/parser.y b/MathEval/parser.y
index 7c3d250b11ac510474b1de58d6b73bf4a6e9cfe5..10db82c2c726d5c90e48f21840fd68320657d078 100644
--- a/MathEval/parser.y
+++ b/MathEval/parser.y
@@ -35,6 +35,13 @@ int yyerror (char *s);
 /* Function used to tokenize string representing function (this function
    is generated by scanner generator).  */
 int yylex (void);
+
+/* Function used to flush the internal flex buffer when we exit
+   prematurely (i.e., in case of a parse error) so that the next time
+   we call the scanner, all is nicely reset. Without this, the
+   behaviour of the next call after an error is unpredictable.  */
+int force_buffer_flush(void);
+
 %}
 
 /* Parser semantic values type.  */
@@ -63,7 +70,6 @@ int yylex (void);
 input
 : expression '\n' {
   matheval_root = $1;
-  yyerrok;
   return 1;
 }
 ;
@@ -115,5 +121,6 @@ int yyerror(char* s)
   /* Indicate parsing error through appropriate flag and stop
      parsing.  */
   matheval_ok = 0;
+  force_buffer_flush();
   return 0;
 }
diff --git a/MathEval/scanner.cpp b/MathEval/scanner.cpp
index 67e95880ad72f84f8e11308a8f77ccf583c61a39..004b773591e7d1fe89979046efa110f41e2c559f 100644
--- a/MathEval/scanner.cpp
+++ b/MathEval/scanner.cpp
@@ -20,7 +20,7 @@
 /* A lexical scanner generated by flex */
 
 /* Scanner skeleton version:
- * $Header: /cvsroot/gmsh/MathEval/scanner.cpp,v 1.3 2004-05-12 18:38:44 geuzaine Exp $
+ * $Header: /cvsroot/gmsh/MathEval/scanner.cpp,v 1.4 2004-05-12 18:57:48 geuzaine Exp $
  */
 
 #define FLEX_SCANNER
@@ -1687,7 +1687,7 @@ int main()
 
 #undef mewrap
 
-int mewrap() {return 1;}
+int mewrap() { return 1; }
 
 static int input_from_string (char *buffer, int max_size)
 {
@@ -1704,3 +1704,5 @@ static int input_from_string (char *buffer, int max_size)
 
   return count;
 }
+
+int force_buffer_flush() { YY_FLUSH_BUFFER; }
diff --git a/MathEval/scanner.l b/MathEval/scanner.l
index 8c6977fd41b83d043d1f58c0cdcd7b3ceacae71c..b060e2b5e142ce04d8c2d89b17cbe1276c499873 100644
--- a/MathEval/scanner.l
+++ b/MathEval/scanner.l
@@ -107,7 +107,7 @@ identifier [a-zA-Z\_][a-zA-Z0-9\_]*
 
 #undef mewrap
 
-int mewrap() {return 1;}
+int mewrap() { return 1; }
 
 static int input_from_string (char *buffer, int max_size)
 {
@@ -124,3 +124,5 @@ static int input_from_string (char *buffer, int max_size)
 
   return count;
 }
+
+int force_buffer_flush() { YY_FLUSH_BUFFER; }