diff --git a/cores/esp8266/Arduino.h b/cores/esp8266/Arduino.h
index 6b9aedcfb..19c25e899 100644
--- a/cores/esp8266/Arduino.h
+++ b/cores/esp8266/Arduino.h
@@ -186,48 +186,4 @@ long map(long, long, long, long, long);
 
 #include "pins_arduino.h"
 
-/**
- * User-defined Literals
- *  usage:
- *
- *   uint32_t = test = 10_MHz; // --> 10000000
- */
-#ifdef __cplusplus
-unsigned long long operator"" _kHz(unsigned long long x) {
-    return x * 1000;
-}
-
-unsigned long long operator"" _MHz(unsigned long long x) {
-    return x * 1000 * 1000;
-}
-
-unsigned long long operator"" _GHz(unsigned long long x) {
-    return x * 1000 * 1000 * 1000;
-}
-
-unsigned long long operator"" _kBit(unsigned long long x) {
-    return x * 1024;
-}
-
-unsigned long long operator"" _MBit(unsigned long long x) {
-    return x * 1024 * 1024;
-}
-
-unsigned long long operator"" _GBit(unsigned long long x) {
-    return x * 1024 * 1024 * 1024;
-}
-
-unsigned long long operator"" _kB(unsigned long long x) {
-    return x * 1024;
-}
-
-unsigned long long operator"" _MB(unsigned long long x) {
-    return x * 1024 * 1024;
-}
-
-unsigned long long operator"" _GB(unsigned long long x) {
-    return x * 1024 * 1024 * 1024;
-}
-#endif
-
 #endif
diff --git a/cores/esp8266/Esp.cpp b/cores/esp8266/Esp.cpp
index 5dafde53e..26f31bb4c 100644
--- a/cores/esp8266/Esp.cpp
+++ b/cores/esp8266/Esp.cpp
@@ -29,6 +29,50 @@ extern "C" void ets_wdt_enable(void);
 extern "C" void ets_wdt_disable(void);
 extern "C" void wdt_feed(void);
 
+/**
+ * User-defined Literals
+ *  usage:
+ *
+ *   uint32_t = test = 10_MHz; // --> 10000000
+ */
+
+unsigned long long operator"" _kHz(unsigned long long x) {
+    return x * 1000;
+}
+
+unsigned long long operator"" _MHz(unsigned long long x) {
+    return x * 1000 * 1000;
+}
+
+unsigned long long operator"" _GHz(unsigned long long x) {
+    return x * 1000 * 1000 * 1000;
+}
+
+unsigned long long operator"" _kBit(unsigned long long x) {
+    return x * 1024;
+}
+
+unsigned long long operator"" _MBit(unsigned long long x) {
+    return x * 1024 * 1024;
+}
+
+unsigned long long operator"" _GBit(unsigned long long x) {
+    return x * 1024 * 1024 * 1024;
+}
+
+unsigned long long operator"" _kB(unsigned long long x) {
+    return x * 1024;
+}
+
+unsigned long long operator"" _MB(unsigned long long x) {
+    return x * 1024 * 1024;
+}
+
+unsigned long long operator"" _GB(unsigned long long x) {
+    return x * 1024 * 1024 * 1024;
+}
+
+
 EspClass ESP;
 
 EspClass::EspClass()