diff --git a/libguile/Makefile.am b/libguile/Makefile.am
index 3987240f0..e2a5d82e9 100644
--- a/libguile/Makefile.am
+++ b/libguile/Makefile.am
@@ -185,7 +185,7 @@ SUFFIXES = .x .doc
 	PATH=.:${PATH} ./guile-doc-snarf $< $(DEFS) $(INCLUDES) $(CPPFLAGS) $(CFLAGS) $< > $@ \
 	|| { rm $@; false; }
 .x.doc: 
-	PATH=.:${PATH} ./guile-doc-snarf $*.c $(DEFS) $(INCLUDES) $(CPPFLAGS) $(CFLAGS) $*.c > /dev/null \
+	PATH=.:${PATH} ./guile-doc-snarf $(srcdir)/$*.c $(DEFS) $(INCLUDES) $(CPPFLAGS) $(CFLAGS) $(srcdir)/$*.c > /dev/null \
         || { rm $@; false; }
 
 error.x: cpp_err_symbols.c