diff --git a/Marlin/src/core/serial.h b/Marlin/src/core/serial.h
index 00ef03bc70..c878a0fc29 100644
--- a/Marlin/src/core/serial.h
+++ b/Marlin/src/core/serial.h
@@ -53,8 +53,8 @@ extern uint8_t marlin_debug_flags;
   #define _PORT_REDIRECT(n,p)   REMEMBER(n,serial_port_index,p)
   #define _PORT_RESTORE(n)      RESTORE(n)
   #define SERIAL_OUT(WHAT, V...) do{ \
-    if (!serial_port_index || serial_port_index == SERIAL_BOTH) (void)MYSERIAL0.WHAT(V); \
-    if ( serial_port_index) (void)MYSERIAL1.WHAT(V); \
+    if (!serial_port_index || serial_port_index == SERIAL_BOTH || serial_port_index == -1) (void)MYSERIAL0.WHAT(V); \
+    if ( serial_port_index ) (void)MYSERIAL1.WHAT(V); \
   }while(0)
   #define SERIAL_ASSERT(P)      if(serial_port_index!=(P)){ debugger(); }
 #else
@@ -69,7 +69,7 @@ extern uint8_t marlin_debug_flags;
 
 #if ENABLED(MKS_WIFI)
 #define SERIAL_ECHO(x) do{ \
-    if (!serial_port_index || serial_port_index == SERIAL_BOTH) SERIAL_OUT(print, x); \
+    if (!serial_port_index || serial_port_index == SERIAL_BOTH || serial_port_index == -1 ) SERIAL_OUT(print, x); \
     if ( serial_port_index) mks_wifi_print(x); \
   }while(0)
 #else
@@ -80,7 +80,7 @@ extern uint8_t marlin_debug_flags;
 
 #if ENABLED(MKS_WIFI)
 #define SERIAL_ECHOLN(x) do{ \
-    if (!serial_port_index || serial_port_index == SERIAL_BOTH) SERIAL_OUT(println, x); \
+    if (!serial_port_index || serial_port_index == SERIAL_BOTH || serial_port_index == -1) SERIAL_OUT(println, x); \
     if ( serial_port_index) mks_wifi_println(x); \
   }while(0)
 #else
@@ -116,7 +116,7 @@ extern uint8_t marlin_debug_flags;
 
 #if ENABLED(MKS_WIFI)
 #define SERIAL_CHAR(V...) do{ \
-    if (!serial_port_index || serial_port_index == SERIAL_BOTH) _CHAR_N(NUM_ARGS(V),V); \
+    if (!serial_port_index || serial_port_index == SERIAL_BOTH || serial_port_index == -1) _CHAR_N(NUM_ARGS(V),V); \
     if ( serial_port_index) mks_wifi_print_var(NUM_ARGS(V),V); \
   }while(0)
 #else
diff --git a/Marlin/src/core/types.h b/Marlin/src/core/types.h
index 1212eb5ba2..6bcd4bd489 100644
--- a/Marlin/src/core/types.h
+++ b/Marlin/src/core/types.h
@@ -347,14 +347,14 @@ struct XYZval {
   FI XYZval<T>  operator* (const XYZEval<T> &rs)       { XYZval<T> ls = *this; ls.x *= rs.x; ls.y *= rs.y; ls.z *= rs.z; return ls; }
   FI XYZval<T>  operator/ (const XYZEval<T> &rs) const { XYZval<T> ls = *this; ls.x /= rs.x; ls.y /= rs.y; ls.z /= rs.z; return ls; }
   FI XYZval<T>  operator/ (const XYZEval<T> &rs)       { XYZval<T> ls = *this; ls.x /= rs.x; ls.y /= rs.y; ls.z /= rs.z; return ls; }
-  FI XYZval<T>  operator* (const float &v)       const { XYZval<T> ls = *this; ls.x *= v;    ls.y *= v;    ls.z *= z;    return ls; }
-  FI XYZval<T>  operator* (const float &v)             { XYZval<T> ls = *this; ls.x *= v;    ls.y *= v;    ls.z *= z;    return ls; }
-  FI XYZval<T>  operator* (const int &v)         const { XYZval<T> ls = *this; ls.x *= v;    ls.y *= v;    ls.z *= z;    return ls; }
-  FI XYZval<T>  operator* (const int &v)               { XYZval<T> ls = *this; ls.x *= v;    ls.y *= v;    ls.z *= z;    return ls; }
-  FI XYZval<T>  operator/ (const float &v)       const { XYZval<T> ls = *this; ls.x /= v;    ls.y /= v;    ls.z /= z;    return ls; }
-  FI XYZval<T>  operator/ (const float &v)             { XYZval<T> ls = *this; ls.x /= v;    ls.y /= v;    ls.z /= z;    return ls; }
-  FI XYZval<T>  operator/ (const int &v)         const { XYZval<T> ls = *this; ls.x /= v;    ls.y /= v;    ls.z /= z;    return ls; }
-  FI XYZval<T>  operator/ (const int &v)               { XYZval<T> ls = *this; ls.x /= v;    ls.y /= v;    ls.z /= z;    return ls; }
+  FI XYZval<T>  operator* (const float &v)       const { XYZval<T> ls = *this; ls.x *= v;    ls.y *= v;    ls.z *= v;    return ls; }
+  FI XYZval<T>  operator* (const float &v)             { XYZval<T> ls = *this; ls.x *= v;    ls.y *= v;    ls.z *= v;    return ls; }
+  FI XYZval<T>  operator* (const int &v)         const { XYZval<T> ls = *this; ls.x *= v;    ls.y *= v;    ls.z *= v;    return ls; }
+  FI XYZval<T>  operator* (const int &v)               { XYZval<T> ls = *this; ls.x *= v;    ls.y *= v;    ls.z *= v;    return ls; }
+  FI XYZval<T>  operator/ (const float &v)       const { XYZval<T> ls = *this; ls.x /= v;    ls.y /= v;    ls.z /= v;    return ls; }
+  FI XYZval<T>  operator/ (const float &v)             { XYZval<T> ls = *this; ls.x /= v;    ls.y /= v;    ls.z /= v;    return ls; }
+  FI XYZval<T>  operator/ (const int &v)         const { XYZval<T> ls = *this; ls.x /= v;    ls.y /= v;    ls.z /= v;    return ls; }
+  FI XYZval<T>  operator/ (const int &v)               { XYZval<T> ls = *this; ls.x /= v;    ls.y /= v;    ls.z /= v;    return ls; }
   FI XYZval<T>  operator>>(const int &v)         const { XYZval<T> ls = *this; _RS(ls.x); _RS(ls.y); _RS(ls.z); return ls; }
   FI XYZval<T>  operator>>(const int &v)               { XYZval<T> ls = *this; _RS(ls.x); _RS(ls.y); _RS(ls.z); return ls; }
   FI XYZval<T>  operator<<(const int &v)         const { XYZval<T> ls = *this; _LS(ls.x); _LS(ls.y); _LS(ls.z); return ls; }