diff --git a/mypyc/lib-rt/librt_internal.h b/mypyc/lib-rt/librt_internal.h
index 329a0fd68c11..bef9e196d2c1 100644
--- a/mypyc/lib-rt/librt_internal.h
+++ b/mypyc/lib-rt/librt_internal.h
@@ -64,7 +64,12 @@ import_librt_internal(void)
         return -1;
     memcpy(NativeInternal_API, capsule, sizeof(NativeInternal_API));
     if (NativeInternal_ABI_Version() != LIBRT_INTERNAL_ABI_VERSION) {
-        PyErr_SetString(PyExc_ValueError, "ABI version conflict for librt.internal");
+        char err[128];
+        snprintf(err, sizeof(err), "ABI version conflict for librt.internal, expected %d, found %d",
+            LIBRT_INTERNAL_ABI_VERSION,
+            NativeInternal_ABI_Version()
+        );
+        PyErr_SetString(PyExc_ValueError, err);
         return -1;
     }
     return 0;