diff --git a/tests/plat/b/incdec_b.b b/tests/plat/b/incdec_b.b
index b3cb16da5..4edf5f6bf 100644
--- a/tests/plat/b/incdec_b.b
+++ b/tests/plat/b/incdec_b.b
@@ -1,65 +1,70 @@
 #
+/* External variables to defeat constant folding. */
+zero 0;
+one 1;
+
 i 0;
 
 ext_t()
 {
-    extrn i;
+    extrn zero, one, i;
 
-	i = 0;
+	i = zero;
 	if (!(i++ == 0)) fail(__LINE__);
 
-	i == 1;
+	i = one;
 	if (!(i-- == 1)) fail(__LINE__);
 	if (!(i == 0)) fail(__LINE__);
 
-	i = 0;
+	i = zero;
 	if (!(++i == 1)) fail(__LINE__);
 	if (!(i == 1)) fail(__LINE__);
 
-	i == 1;
+	i = one;
 	if (!(--i == 0)) fail(__LINE__);
 	if (!(i == 0)) fail(__LINE__);
 }
 
 int_t()
 {
-    auto i;
+    extrn zero, one;
+	auto i;
 
-	i = 0;
+	i = zero;
 	if (!(i++ == 0)) fail(__LINE__);
 
-	i == 1;
+	i = one;
 	if (!(i-- == 1)) fail(__LINE__);
 	if (!(i == 0)) fail(__LINE__);
 
-	i = 0;
+	i = zero;
 	if (!(++i == 1)) fail(__LINE__);
 	if (!(i == 1)) fail(__LINE__);
 
-	i == 1;
+	i = one;
 	if (!(--i == 0)) fail(__LINE__);
 	if (!(i == 0)) fail(__LINE__);
 }
 
 star_t()
 {
-    extrn i;
+    extrn zero, one, i;
     auto p;
 
     p = &i;
 
-	i = 0;
+	i = zero;
     if (!((*p)++ == 0)) fail(__LINE__);
 
-	i == 1;
+	i = one;
     if (!((*p)-- == 1)) fail(__LINE__);
 	if (!(i == 0)) fail(__LINE__);
 
-	i = 0;
+	i = zero;
     if (!(++(*p) == 1)) fail(__LINE__);
 	if (!(i == 1)) fail(__LINE__);
 
-	i == 1;
+	i = one;
     if (!(--(*p) == 0)) fail(__LINE__);
 	if (!(i == 0)) fail(__LINE__);
 }