diff --git a/configure.ac b/configure.ac
index acd397e66..4ac30e8a1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -124,6 +124,13 @@ if test "$gl_gcc_warnings" = yes; then
   nw="$nw -Wold-style-definition"
   gl_MANYWARN_COMPLEMENT([GNULIB_WARN_CFLAGS], [$WARN_CFLAGS], [$nw])
   AC_SUBST([GNULIB_WARN_CFLAGS])
+
+  # For gnulib-tests, the set is slightly smaller still.
+  nw=
+  nw="$nw -Wstrict-prototypes"
+  gl_MANYWARN_COMPLEMENT([GNULIB_TEST_WARN_CFLAGS],
+                         [$GNULIB_WARN_CFLAGS], [$nw])
+  AC_SUBST([GNULIB_TEST_WARN_CFLAGS])
 fi
 
 AC_FUNC_FORK
diff --git a/gnulib-tests/Makefile.am b/gnulib-tests/Makefile.am
index c3a48e841..7ec0a1cdd 100644
--- a/gnulib-tests/Makefile.am
+++ b/gnulib-tests/Makefile.am
@@ -1,3 +1,17 @@
 include gnulib.mk
 
-AM_CFLAGS = $(GNULIB_WARN_CFLAGS) # $(WERROR_CFLAGS)
+AM_CFLAGS = $(GNULIB_TEST_WARN_CFLAGS) # $(WERROR_CFLAGS)
+
+# A few tests are inherently warning-evoking.
+# Since we require -Werror, exempt the few offenders.
+
+# test-xvasprintf.c: In function 'test_xasprintf':
+# test-xvasprintf.c:100: error: format not a string literal and no \
+#   format arguments [-Wformat-security]
+test_xvasprintf_CFLAGS = $(AM_CFLAGS) -Wno-format-security
+
+# test-lock.c: In function 'lock_mutator_thread':
+# test-lock.c:148: error: cast from function call of type 'pthread_t' to \
+#   non-matching type 'void *' [-Wbad-function-cast]
+test_lock_CFLAGS = $(AM_CFLAGS) -Wno-bad-function-cast
+test_tls_CFLAGS = $(AM_CFLAGS) -Wno-bad-function-cast