diff --git a/src/cc65/litpool.c b/src/cc65/litpool.c
index 6d8827c60..381073d23 100644
--- a/src/cc65/litpool.c
+++ b/src/cc65/litpool.c
@@ -470,6 +470,7 @@ Literal* AddLiteral (const char* S)
 {
     StrBuf SB;
     SB_InitFromString(&SB, S);
+    SB_AppendChar(&SB, '\0');
     return AddLiteralStr(&SB);
 }
 
diff --git a/test/val/bug2920.c b/test/val/bug2920.c
new file mode 100644
index 000000000..4267c0a76
--- /dev/null
+++ b/test/val/bug2920.c
@@ -0,0 +1,20 @@
+#include "unittest.h"
+
+TEST {
+    /* The bug causes __func__ to be not null terminated. */
+    const char *f = __func__;
+    size_t size = sizeof(__func__);
+    size_t i;
+
+    /* Ensure the size is correct (5 for "main" + null terminator) */
+    ASSERT_AreEqual((unsigned)size, 5u, "%u", "Sizeof __func__ should be 5");
+
+    /* Check content */
+    for (i = 0; i < size - 1; ++i) {
+        ASSERT_AreEqual(f[i], "main"[i], "%c", "Character mismatch");
+    }
+
+    /* Check null terminator specifically */
+    ASSERT_AreEqual(f[size - 1], '\0', "%02X", "Null terminator missing");
+}
+ENDTEST