diff --git a/ChangeLog b/ChangeLog
index 4b16516d1..ac0ad57e7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2010-09-15  Werner Lemberg  <wl@gnu.org>
+
+	Make bytecode debugging with FontForge work again.
+
+	* src/truetype/ttinterp.c (TT_RunIns): Don't call
+	`free_buffer_in_size' in case of error if a debugger is active.
+
 2010-09-14  Werner Lemberg  <wl@gnu.org>
 
 	Improve tracing messages.
diff --git a/src/truetype/ttinterp.c b/src/truetype/ttinterp.c
index a3eeaa69b..64010091e 100644
--- a/src/truetype/ttinterp.c
+++ b/src/truetype/ttinterp.c
@@ -8162,13 +8162,15 @@
     *exc = cur;
 #endif
 
-    /* if any errors, function tables may be broken.  */
-    /* it should not be used for next interpretation. */
-    if ( CUR.error )
+    /* If any errors have occurred, function tables may be broken. */
+    /* Force a re-execution of `prep' and `fpgm' tables if no      */
+    /* bytecode debugger is run.                                   */
+    if ( CUR.error && !CUR.instruction_trap )
     {
       FT_TRACE1(( "  The interpreter returned error 0x%x\n", CUR.error ));
       free_buffer_in_size( exc );
-      exc->size->cvt_ready = FALSE;  
+
+      exc->size->cvt_ready      = FALSE;  
       exc->size->bytecode_ready = FALSE;  
     }