diff --git a/cores/esp32/WString.cpp b/cores/esp32/WString.cpp
index 71183213ac2..14b40e3ae34 100644
--- a/cores/esp32/WString.cpp
+++ b/cores/esp32/WString.cpp
@@ -239,15 +239,18 @@ String &String::copy(const char *cstr, unsigned int length) {
 void String::move(String &rhs) {
   if (buffer()) {
     if (capacity() >= rhs.len()) {
-      memmove(wbuffer(), rhs.buffer(), rhs.length() + 1);
+      // Use case: When 'reserve()' was called and the first
+      // assignment/append is the return value of a function.
+      if (rhs.len() && rhs.buffer()) {
+        memmove(wbuffer(), rhs.buffer(), rhs.length());
+      }
       setLen(rhs.len());
       rhs.invalidate();
       return;
-    } else {
-      if (!isSSO()) {
-        free(wbuffer());
-        setBuffer(nullptr);
-      }
+    }
+    if (!isSSO()) {
+      free(wbuffer());
+      setBuffer(nullptr);
     }
   }
   if (rhs.isSSO()) {
@@ -259,10 +262,7 @@ void String::move(String &rhs) {
   }
   setCapacity(rhs.capacity());
   setLen(rhs.len());
-  rhs.setSSO(false);
-  rhs.setCapacity(0);
-  rhs.setBuffer(nullptr);
-  rhs.setLen(0);
+  rhs.init();
 }
 #endif