diff --git a/ChangeLog b/ChangeLog
index 91d5f3cf..176c8ff1 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2000-11-02  Akim Demaille  <akim@epita.fr>
+
+	* tests/tools.at (Tracing M4 builtins): New test.
+	* autoconh.sh (trace_format): Fix its computation.
+
 2000-11-02  Akim Demaille  <akim@epita.fr>
 
 	* tests/atgeneral.m4 (AT_CHECK): Check stderr first, since if both
@@ -9,7 +14,7 @@
 	* autoconf.sh (task trace) [debug]: Instead of a long pipe, extend
 	trace.m4.
 
-	
+
 2000-11-02  Akim Demaille  <akim@epita.fr>
 
 	* autoupdate.sh (m4.txt): Use `dumpdef' and m4 to build it.
diff --git a/autoconf.in b/autoconf.in
index 7017bd7c..dec6e061 100644
--- a/autoconf.in
+++ b/autoconf.in
@@ -570,7 +570,14 @@ EOF
   do
     # The request may be several lines long, hence sed has to quit.
     macro_name=`echo "$trace" | sed 's/:.*//;q'`
-    trace_format=`echo "$trace" | sed '1s/^[^:]*:/:/'`
+    # If for instance TRACE is `define', be sure to have an empty
+    # TRACE_FORMAT.
+    case $trace in
+      $macro_name:* )
+         trace_format=`echo "$trace" | sed "1s/^$macro_name:/:/"`;;
+      * )
+         trace_format=;;
+    esac
 
     # GNU M4 1.4's tracing of builtins is buggy.  When run on this input:
     #
diff --git a/autoconf.sh b/autoconf.sh
index 7017bd7c..dec6e061 100644
--- a/autoconf.sh
+++ b/autoconf.sh
@@ -570,7 +570,14 @@ EOF
   do
     # The request may be several lines long, hence sed has to quit.
     macro_name=`echo "$trace" | sed 's/:.*//;q'`
-    trace_format=`echo "$trace" | sed '1s/^[^:]*:/:/'`
+    # If for instance TRACE is `define', be sure to have an empty
+    # TRACE_FORMAT.
+    case $trace in
+      $macro_name:* )
+         trace_format=`echo "$trace" | sed "1s/^$macro_name:/:/"`;;
+      * )
+         trace_format=;;
+    esac
 
     # GNU M4 1.4's tracing of builtins is buggy.  When run on this input:
     #
diff --git a/bin/autoconf.in b/bin/autoconf.in
index 7017bd7c..dec6e061 100644
--- a/bin/autoconf.in
+++ b/bin/autoconf.in
@@ -570,7 +570,14 @@ EOF
   do
     # The request may be several lines long, hence sed has to quit.
     macro_name=`echo "$trace" | sed 's/:.*//;q'`
-    trace_format=`echo "$trace" | sed '1s/^[^:]*:/:/'`
+    # If for instance TRACE is `define', be sure to have an empty
+    # TRACE_FORMAT.
+    case $trace in
+      $macro_name:* )
+         trace_format=`echo "$trace" | sed "1s/^$macro_name:/:/"`;;
+      * )
+         trace_format=;;
+    esac
 
     # GNU M4 1.4's tracing of builtins is buggy.  When run on this input:
     #
diff --git a/tests/tools.at b/tests/tools.at
index c83bc785..9ddf2346 100644
--- a/tests/tools.at
+++ b/tests/tools.at
@@ -244,12 +244,15 @@ AT_CLEANUP
 ## autoconf --trace.  ##
 ## ------------------ ##
 
+
+# Tracing user defined macros
+# ---------------------------
 AT_SETUP(autoconf --trace)
 
 AT_DATA(configure.in,
-[[define(active, ACTIVE)
-AC_DEFUN(TRACE1, [TRACE2(m4_shift($@))])
-AC_DEFUN(TRACE2, [[$2], $1])
+[[define([active], [ACTIVE])
+AC_DEFUN([TRACE1], [TRACE2(m4_shift($@))])
+AC_DEFUN([TRACE2], [[$2], $1])
 TRACE1(foo, bar, baz)
 TRACE1(foo, AC_TRACE1(bar, baz))
 TRACE1(foo, active, baz)
@@ -297,6 +300,31 @@ AT_CHECK([autoconf --autoconf-dir .. -l $at_srcdir -t TRACE2:'${)===(}@'], 0,
 AT_CLEANUP
 
 
+# Tracing builtins
+# ----------------
+AT_SETUP(Tracing M4 builtins)
+
+AT_DATA(configure.in,
+[[define([active], [ACTIVE])
+]])
+
+AT_CHECK([[autoconf --autoconf-dir .. -l $at_srcdir -t define |
+            sed -n '$p']],
+         0,
+[[configure.in:1:define:active:ACTIVE
+]])
+
+# FIXME: Without `$1' the following test dies.  Groumphf, once again to
+# dive into obscure feature interaction...
+AT_CHECK([[autoconf --autoconf-dir .. -l $at_srcdir -t define:'$1' -i |
+            sed -n '$p']],
+         0,
+[[active
+]])
+
+AT_CLEANUP
+
+
 
 
 ## ----------------------------------------------- ##