diff --git a/exebuf.c b/exebuf.c
index f4d0772b..331f3095 100644
--- a/exebuf.c
+++ b/exebuf.c
@@ -151,7 +151,7 @@ static pDynString findBlockEnd(pExeBuf self)
 {
   pDynString command = NULL;
   char *buffer = NULL;
-  int i;
+  int i, j;
 
   assert(self);
 
@@ -163,7 +163,8 @@ static pDynString findBlockEnd(pExeBuf self)
   if (self->end != -1) {
     self->start = self->end + 1;
   }
-  for (i = self->start; i < strlen(buffer); i++) {
+  j = strlen(buffer);
+  for (i = self->start; i < j; i++) {
     DynStringConcatChar(command, buffer[i]);
     if (buffer[i] == '\n') {
       self->lineno++;