diff --git a/ChangeLog b/ChangeLog
index a5d8d7e85..e2d561105 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,8 @@
 2015-04-15  Peter Stephenson  <p.stephenson@samsung.com>
 
+	* 34892 (slightly tweaked): Src/math.c, Test/C01arith.ztst: fix
+	math evaluation with empty expression resulting from substitution.
+
 	* 34887: Src/exec, Test/E01options.ztst: assignments before
 	"command special-builtin/func" in POSIX_BUILTINS mode behave as
 	normal command. Tidy up case handling in code and add test.
diff --git a/Src/math.c b/Src/math.c
index c047725c5..2105180c8 100644
--- a/Src/math.c
+++ b/Src/math.c
@@ -1398,7 +1398,7 @@ matheval(char *s)
     if (!mlevel)
 	outputradix = outputunderscore = 0;
 
-    if (!*s) {
+    if (!*s || *s == Nularg) {
 	x.type = MN_INTEGER;
 	x.u.l = 0;
 	return x;
@@ -1435,7 +1435,7 @@ mathevalarg(char *s, char **ss)
      *
      * To avoid a more opaque error further in, bail out here.
      */
-    if (!*s) {
+    if (!*s || *s == Nularg) {
 	zerr("bad math expression: empty string");
 	return (zlong)0;
     }
diff --git a/Test/C01arith.ztst b/Test/C01arith.ztst
index d3176dd5e..e2dfe56fc 100644
--- a/Test/C01arith.ztst
+++ b/Test/C01arith.ztst
@@ -383,4 +383,7 @@
   print ${$(( $1 * 100 ))%%.[0-9]#})
 0:Arithmetic substitution nested in parameter substitution
 >3246
- 
+
+  print $((`:`))
+0:Null string in arithmetic evaluation after command substitution
+>0