diff --git a/tests/libtest/Makefile.am b/tests/libtest/Makefile.am
index 03eeb06dad..d14f37d39e 100644
--- a/tests/libtest/Makefile.am
+++ b/tests/libtest/Makefile.am
@@ -51,6 +51,8 @@ CFLAG_CURL_SYMBOL_HIDING = @CFLAG_CURL_SYMBOL_HIDING@
 
 CFLAGS += @CURL_CFLAG_EXTRAS@
 
+CLEANFILES = lib1521.c
+
 # Prevent LIBS from being used for all link targets
 LIBS = $(BLANK_AT_MAKETIME)