2 files changed, 7 insertions, 1 deletions
diff --git a/t/lib/h2ph.h b/t/lib/h2ph.h
index 23f259e37e..78429ca310 100644
--- a/t/lib/h2ph.h
+++ b/t/lib/h2ph.h
@@ -26,6 +26,10 @@
 #undef MAX
 #define MAX(a,b) ((a) > (b) ? (a) : (b))
 
+/* Test #undef'ining an existing constant function */
+#define NOTTRUE 0
+#undef NOTTRUE
+
 /* Test #ifdef */
 #ifdef __SOME_UNIMPORTANT_PROPERTY
 #define MIN(a,b) ((a) < (b) ? (a) : (b))
diff --git a/t/lib/h2ph.pht b/t/lib/h2ph.pht
index 01db98d523..3723fca84a 100644
--- a/t/lib/h2ph.pht
+++ b/t/lib/h2ph.pht
@@ -1,6 +1,6 @@
 require '_h2ph_pre.ph';
 
-no warnings 'redefine';
+no warnings qw(redefine misc);
 
 unless(defined(&SQUARE)) {
     sub SQUARE {
@@ -22,6 +22,8 @@ unless(defined(&_H2PH_H_)) {
         my($a,$b) = @_;
 	    eval q((($a) > ($b) ? ($a) : ($b)));
     }' unless defined(&MAX);
+    eval 'sub NOTTRUE () {0;}' unless defined(&NOTTRUE);
+    undef(&NOTTRUE) if defined(&NOTTRUE);
     if(defined(&__SOME_UNIMPORTANT_PROPERTY)) {
 	eval 'sub MIN {
 	    my($a,$b) = @_;