diff --git a/include/decimal.h b/include/decimal.h
index 5b5b8c0b460..fddae1f54a6 100644
--- a/include/decimal.h
+++ b/include/decimal.h
@@ -51,13 +51,7 @@ int decimal_mul(decimal *from1, decimal *from2, decimal *to);
 int decimal_div(decimal *from1, decimal *from2, decimal *to, int scale_incr);
 int decimal_mod(decimal *from1, decimal *from2, decimal *to);
 int decimal_round(decimal *from, decimal *to, int new_scale, decimal_round_mode mode);
-
-/*
-  the following works only on special "zero" decimal, not on any
-  decimal that happen to evaluate to zero
-*/
-
-#define decimal_is_zero(dec) ((dec)->intg1==1 && (dec)->frac1==0 && (dec)->buf[0]==0)
+int decimal_is_zero(decimal *from);
 
 /* set a decimal to zero */
 
diff --git a/strings/decimal.c b/strings/decimal.c
index 6b2982d8d8f..2dcc2c88ceb 100644
--- a/strings/decimal.c
+++ b/strings/decimal.c
@@ -1240,6 +1240,16 @@ int decimal_cmp(decimal *from1, decimal *from2)
   return from1->sign > from2->sign ? -1 : 1;
 }
 
+int decimal_is_zero(decimal *from)
+{
+  dec1 *buf1=from->buf,
+       *end=buf1+ROUND_UP(from->intg)+ROUND_UP(from->frac);
+  while (buf1 < end)
+    if (*buf1++)
+      return 0;
+  return 1;
+}
+
 /*
   multiply two decimals