diff --git a/scripts/runqemu b/scripts/runqemu
index 69cd44864e..f350021258 100755
--- a/scripts/runqemu
+++ b/scripts/runqemu
@@ -1483,7 +1483,7 @@ to your build configuration.
         # If no serial or serialtcp options were specified, only ttyS0 is created
         # and sysvinit shows an error trying to enable ttyS1:
         #     INIT: Id "S1" respawning too fast: disabled for 5 minutes
-        serial_num = len(re.findall("-serial", self.qemu_opt))
+        serial_num = len(re.findall("(^| )-serial ", self.qemu_opt))
 
         # Assume if the user passed serial options, they know what they want
         # and pad to two devices
@@ -1503,7 +1503,7 @@ to your build configuration.
 
                 self.qemu_opt += " %s" % self.get("QB_SERIAL_OPT")
 
-        serial_num = len(re.findall("-serial", self.qemu_opt))
+        serial_num = len(re.findall("(^| )-serial ", self.qemu_opt))
         if serial_num < 2:
             self.qemu_opt += " -serial null"