diff --git a/Makefile.am b/Makefile.am
index 71414447d..12d34cda8 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -143,9 +143,6 @@ check-ls-dircolors:
 # current locale considers to be equal.
 ASSORT = LC_ALL=C sort
 
-# Extract all lines up to the first one starting with "##".
-prologue = perl -ne '/^\#\#/ and exit; print' $(srcdir)/THANKS.in
-
 # FIXME: avoid dependency to build our own 'sort' for 'make dist' ...
 # when common platforms have a functional case-folding implementation:
 #   $ test 'abácad' = "$(printf '%s\n' 'ab' 'ác' 'ad' \
@@ -157,7 +154,7 @@ prologue = perl -ne '/^\#\#/ and exit; print' $(srcdir)/THANKS.in
 THANKS: THANKS.in Makefile.am .mailmap thanks-gen .version
 	$(AM_V_GEN)rm -f $@-t $@;					\
 	{								\
-	  $(prologue); echo;						\
+	  perl -ne '/^\#\#/ and exit; print' $(srcdir)/THANKS.in; echo;	\
 	  { perl -ne '/^$$/.../^$$/ and !/^$$/ and s/  +/\0/ and print'	\
 	      $(srcdir)/THANKS.in;					\
 	    git log --pretty=format:'%aN%x00%aE'			\