diff --git a/Src/Zle/zle_main.c b/Src/Zle/zle_main.c
index 1afb1bf58..d5ad893a4 100644
--- a/Src/Zle/zle_main.c
+++ b/Src/Zle/zle_main.c
@@ -345,11 +345,34 @@ static int kungetsz;
  */
 
 /**/
-void
-ungetbyte(int ch)
-{
-    if (kungetct == kungetsz)
-	kungetbuf = realloc(kungetbuf, kungetsz *= 2);
+void ungetbyte(int ch) {
+    if (kungetbuf == NULL) {
+        // Initialize buffer
+        kungetsz = 1024;  // Default initial size
+        kungetbuf = malloc(kungetsz * sizeof(int));  // Allocate memory
+        if (kungetbuf == NULL) {
+            fprintf(stderr, "Memory allocation failed!\n");
+            return;  // Exit on failure
+        }
+        kungetct = 0;  // Initialize the counter
+    }
+
+    if (kungetct == kungetsz) {
+        // Resize the buffer if it's full
+        int* temp = realloc(kungetbuf, kungetsz * 2 * sizeof(int));  // Try to reallocate memory
+        if (temp == NULL) {
+            fprintf(stderr, "Memory reallocation failed!\n");
+            free(kungetbuf);  // Free the original buffer to prevent memory leak
+            kungetbuf = NULL;  // Nullify pointer for safety
+            kungetsz = 0;      // Reset size
+            kungetct = 0;      // Reset counter
+            return;            // Exit on failure
+        }
+        kungetbuf = temp;  // Update to the new buffer
+        kungetsz *= 2;     // Update size
+    }
+
+    // Add the byte to the buffer
     kungetbuf[kungetct++] = ch;
 }