diff --git a/src/std/link/lnkCalc.c b/src/std/link/lnkCalc.c
index a7ec9126a..c36174aa6 100644
--- a/src/std/link/lnkCalc.c
+++ b/src/std/link/lnkCalc.c
@@ -185,7 +185,7 @@ static jlif_result lnkCalc_string(jlink *pjlink, const char *val, size_t len)
         return jlif_stop;
     }
 
-    postbuf = malloc(INFIX_TO_POSTFIX_SIZE(len));
+    postbuf = malloc(INFIX_TO_POSTFIX_SIZE(len+1));
     if (!postbuf) {
         errlogPrintf("lnkCalc: Out of memory\n");
         return jlif_stop;